1g ^, •Si L `yr 'R(1`` (Cf{^} si^t,W..ii::'`•:'?.:v^-... -:tn ..;^^: t< , ,. :b :^ s0,. .. t: . '::':::... `.. -; ;,.: .'F '.4sia^ '^+ }` i^ "-'^ ^ ' t.a'. ^ -. ,^':. S ^^^,,',y^; ^ :;4,i •_ ... :'. ^a •'•:,.^^.^^^i:ii < 'j^ ^^ ,;i{^ -^ •:. 'e ^ ^l ' \ . '.S i' 1,ele I,,^::' . . , • ;F^: -x^..5 - ` • • :y}: I':^ ^ ^ .t ..tfir :^ris ^'^) •it [ s ^ 1^; ^'!. :•^-f R. a.^.•. *,>..i` :' ^.. F: ^...: . ^.'"^ .rY: 'J t^^'^,''l!^:; il'"^^ ^ . ^.. `^ .le' /I ALCOA 7 1475 SHEET AND PLATE by Stanley J. Cieslak Paul L. Mehr Aluminum Company of America Application Engineering Division Alcoa Center, Pennsylvania 15069 4th Revised Edition 1985 December (Supersedes 1978 February Edition) ALCOA 7475 SHEET AND PLATE INTRODUCTION Alcoa 7475 was developed by the Alcoa Laboratories for sheet and plate applications that require high strength and a high level of guaranteed fracture toughness. The Alcoa patented alloy was registered with the Aluminum Association in 1969. Since then, Alcoa has produced millions of pounds of 7475 sheet and plate for fatigue and fracture-critical components in high-performance aircraft. Alloy 7475 has the highest toughness for a given strength of the current commercially available high strength aircraft alloys. Alloy 7475 sheet and plate products are currently being used for fuselage skins, upper and lower wing skins, wing spars, center wing structure, and fuselage bulkheads for commercial, transport and fighter aircraft. 7475 SHEET between those of bare and two-side clad 7475-T61 sheet. BARE AND ALCLAD 7475 PLATE Alloy 7475 is available as bare and alclad plate in T651, T7651 and T7351 tempers. All three tempers are heat treated, aged and then stress relieved by stretching to achieve the high toughness properties. The T651 temper has been aged to the highest strength level, T7651 is aged past the peak strength level for higher resistance to exfoliation corrosion and T7351 is further aged for high resistance to both exfoliation corrosion and stress-corrosion cracking. The tensile and yield strengths of 7475-T651 and T7651 plate are equal to or 1 ksi (7 MPa) higher than 7075 on a Alloy 7475 is available as bare and alclad sheet in the T61 and T761 tempers. The T61 temper is a variation of the T6 temper and utilizes special thermal practices to produce high toughness. In this condition, 7475 sheet has tensile properties approaching those of 7075-T6, with significantly higher toughness than 7075-T6. Similarly, T761 is a variation of the T76 temper that provides good resistance to exfoliation corrosion and high toughness. In the T761 temper, alloy 7475 will have strength and exfoliation corrosion resistance comparable to 7075-T76 and toughness approaching that of 2024-T3. Corrosion protection for the higher strength 7475-T61 sheet products is provided by one or two sides being clad with 7072 alloy. One side clad 7475-T61 sheet is currently being supplied by Alcoa for a transport aircraft application requiring a combination of high strength, good fracture toughness and corrosion resistance. Property levels of one-side clad 7475-T61 sheet fall temper-for-temper basis while the fracture toughness greatly exceeds that of the established aluminum alloys of comparable strengths. Alloy 7475-T7351 tensile and yield strengths are 1 to 7 ksi (7 to 48 MPa) higher than 7075-T7351 plate depending on plate thickness, and exhibit fracture toughness superior to 2024-T351. Superior tensile properties combined with a high level of resistance to exfoliation and stress-corrosion cracking give 7475-T7351 additional advantages over 2024-T351. CHEMICAL COMPOSITION Composition limits for alloy 7475 are compared with those of 7075 in Table I. Alclad 7475 sheet and plate are The cladding clad with alloy 7072. thicknesses are the same as alloy 7075. One-side clad or two-side clad sheet and plate are available. PHYSICAL PROPERTIES Typical physical properties of 7475 are shown in Table II. 1 ROOM TEMPERATURE MECHANICAL PROPERTIES Tables III and IV list design Mechanical properties for bare and alclad 7475-T61 and T761 sheet. Tables V and VI show Alcoa's proposed new design allowables for 7475-T651, T7651 and T7351 plate. Data is based on analysis of recent production data. These new values will be proposed for inclusion in MIL-HDBK-5D. Typical tensile and compressive stress strain curves and compressive tangent modulus curves for bare 7475-T61 and T761 sheet are shown in Figures 1 through 4. Similar curves for alclad 7475-T61 sheet, 7475-T651, T7651 and T7351 plate are contained in MIL-HDBK5D. MECHANICAL PROPERTIES AT CRYOGENIC AND ELEVATED TEMPERATURES Refer to Tables VII and VIII for typical mechanical properties at various temperatures for bare 7475-T61 and T761 sheet. PROCUREMENT SPECIFICATIONS The Aerospace Material Specifications (AMS) for bare and two-side alclad 7475-T61 and T761 sheet and 7475-T651, T7651 and T7351 plate are shown in Table IX. One-side alclad 7475-T61 sheet is currently being used for a fuselage skin application and is purchased to a customer's in-house specification. Currently, there are no AMS specifications for one-side alclad 7475-T61 and T761 sheet, and material availability is subject to special inquiry. The Aerospace Materials Specifications (AMS) are usuall y the primary specifications for the procurement of 7475 sheet and plate. These AMS specifications require a guaranteed level of fracture toughness (K or K ) with lot acceptance based on minimumnotch-yield i ratios. In the case of 7475-T7351 and 7475-T7651 plate, short rod fracture toughness indicator values or notch yield ratios may be used as lot release criteria. However, there may be design considerations where the fracture toughness requirements need a modification of these acceptance criteria (i.e; K or ). Alcoa can provide correlative cdata to insure that specifications reflect the true fracture toughness characteristics, lot release criteria and mechanical properties. FATIGUE PROPERTIES Modified Goodman Diagrams, which were developed from axial-stress fatigue tests of notched and unnotched specimens of bare and alclad 7475-T61 and T761 sheet, are illustrated in Figures 5 and 6. Figures 7 and 8 show smooth and notched axial stress fatigue data generated from tests conducted on bare 7475T7351 plate. FATIGUE CRACK PROPAGATION Alcoa has conducted extensive, constant amplitude fatigue-crack growth rate (FCGR) tests on 7475 sheet and plate products in various environment:; including air with different degrees of humidity, salt fog and simulated sump tank water. Full range constant amplitude FCGR plots are shown in Figures 9, 10 and 11 for 7475-T651, T7651 and T7351 plate. Figure 12 shows FCGR data for 7475-T7351 plate in two different environments for two plate thicknesses. At near threshold regime, 7475-T651 has a lower rate of fatigue crack propagation than 7475-T7351. At stress intensities above 10 ksi in. (11 MPa the lower rate of fatigue crack propagation of 7475-T7351 compared with 7475-T651 is probably associated with the higher fracture toughness. F), The fatigue crack propagation rates of 7475-T7351 and 2024-T351 plate are similar based on constant amplitude FCGR data. Bare and alclad 7475-T61 and T761 sheet FCGR data are shown in Figures 13 and 14 for various test environments, specimen orientations and sheet thicknesses. These data show that the fatigue crack growth rates of 7475-T61 and 1761 sheet are aimilar. Other data indicate that the fatigue crack propagation rates are similar for bare and alclad 7475 sheet. At higher stress intensities, the fatigue crack propagation of 7475-T61 and T761 is slower than 7075-T6 sheet and comparable to 2024-T3. Fatigue crack growth behavior under spectrum loading is becoming increasingly important in the selection of alloys for fatigue critical aircraft structures. Two recent Naval Air Systems Command contracts (Reference 13 and 14) studied this behavior for a number of high strength 2XXX and 7XXX aluminum alloys for a fighter aircraft load spectra. Some results from these reports are shown in Figure 15. These data show that 7475 has superior fatigue crack growth characteristics for these particular spectra in comparison with 7050 and 7075 in comparable tempers. 7475 SHEET FRACTURE TOUGHNESS ison of 7475's toughness to 7075 is sbown in Figure 18. Alclad 7475-T761 sheet has been the oreferred sheet product for aerospace applications because of its resistance to general and exfoliation corrosion combined with higher toughness in comparison with bare and alclad 7475Figure 17 illustrates K T61. c data for bare and alclad 7475-T761. On the basis of tensile yield strength, Figure 19 shows that 7475 offers a significantly better combination of strength and toughness than 7075-T6. Fracture toughness tests using 16-inch (406.4 mm) wide center-notched panels have been conducted by Alcoa at -65 ` F (-54 C) on six lots of alclad 7475-T761 sheet. The test data are shown along with data from similar tests on bare 2024-T3 and 7075-T6 sheet in Table XI. Results of the tests show an average 25 percent (16 to 36 percent range) reduction in toughness at the subzero temperature compared to room temperature. Similarly, the bare 7075T6 sheet had a 33 percent reduction in K toughness. c To characterize the critical planestress (K c ) fracture toughness of thin material, Alcoa uses a specimen 16 inches (406.4 mm) wide by 44 inches (1117.6 mm) long with a machined 4 inch (101.6 mm) long center crack. This specimen is shown in Figure 16. The test is performed in compliance with ASTM Method B646-78 "Standard Practice for Fracture Toughness Testing of Aluminum Alloys." The analysis of these test data utilizes the crack growth resistance curve (R-curve) concept to describe the material's resistance to fracture during slow stable crack extension. This concept described in ASTM Method E561-81 "Standard Practice for R-Curve Determination" takes into account the growth of the plastic zone as the crack extends from the sharp notch. The K data for 7475 sheet are presented in figure 17. It is important to note that the toughness of 7475 sheet, like that of 2024-T3 sheet, is too high to be fully described by testing 16 inch (406.4 mm) wide panels. Testing of much wider panels to minimize net section yielding would be required to illustrate the full comoarpotential of this material. It has been observed that the critical stress intensity factor, K , from tests of 16 inch (406.4 mm) center-notched panels correlates reasonably well with the notch-yield ratio (notch-tensile strength/tensile yield strength) from tests of 3 inch (76.2 mm) wide edge-notch specimens. (ASTM Method E338, "Standard Method of Sharp Notch Tension Testing of High Strength Sheet Materials.") The correlation between these two parameters, shown in Figure 21, is the basis of Alcoa's less costly notch-tensile sheet product tests for fracture toughness quality control. Alcoa has proposed the minimum values of K and the critical values of notch-yiefd ratio as acceptance criteria for 7475 sheet products which are shown in Table XII. 7475 PLATE FRACTURE TOUGHNESS Plane-strain fracture toughness (K c ) data for 7475 plate were developed I ASTM Method E399 "Standard Method per 250 inches (31. Typical fracture toughness data for 7475 plate are shown in Figure 20 and Table X. to date. The side grooves introduced to the specimen help promote plane-strain conditions during the test.500 inch (12. Figure 23 illustrates the relationship of short rod value to K_ for the 1 inch ( 5.8 mm) in thickness. It can be noted from Table X that 7475 provides a significantly higher level of toughness and hence an appreciably greater crack tolerance than 7075 in corresponding tempers.9 mm) diameter notch-tensile specimens. have been made using the 1 inch (25. Care must be exercised in interpreting the relationships between both the short rod value and value.7 mm) and i.7mm) specimen is used to test material less than 1. The combination of strength and toughness provided by . Alcoa has chosen to quantify the toughness of intermediate thickness products by utilizing a compact tension specimen and the 25 percent secant offset value concept.250 inches (31. tempers. The notch-yield ratio data developed by Alcoa was obtained from tests using the 0.500 inch (12. ASTM Method B645 provides a method in which some invalid data per ASTM Method 7-399 can be considered meaningful.500 inch (12. it is impossible to obtain a valid measure of toughness per ASTM Method F399.060 inch (26.1 mm) thick.for Plane-Strain Fracture Toughness of Metallic Materials" and . designated as in conjunction with ASTM Method 5 I. a quantitative measurement of fracture toughness for lot acceptance and design purposes is more accurately described by crackgrowth resistance curves (R-curves). while the 1.9 mm) specimens provide a more linear and discriminating correlation with the K I values obtained from high toughness a c luminum alloys. Because of the expense involved in making and testing compact specimens (ASTM Method E399).8 mm) in thickness. Other loading devices are equally suitable for performing the test.7 mm) and 1. Results of the short rod test have been found to be extremely linear and correlate well to the Fracture toughness -value _etermined from the compact specimen. A description of the tensile specimen and significance of the notch yield ratio is described in ASTM Method X602-81.750 inch (6.y ield ratio criteria are shown in Table XIII.-.060 inch (26. All of the tests performed by Alcoa. This toughness-strength relationship is superior to that of other high strength aluminum alloys.4-19.4 mm) %475-T7351 snort rod specimen. The lines of contact on the Pracjack grip groove are designed so that the effective load does not change as the specimen mouth is forced open under load. Figure 22) for fracture toughness production quality control and acceptance testing of plate.060 inch (26. between different specimen types and designs and thus are not interchangeable.060 inch (26. The short rod specimen used by Alcoa is the chevron-notched specimen shown in Figure 2 3. "Standard Method for Sharp-Notch Tension Testing with Cylindrical Specimen." It has been found that the notch-yield ratios obtained from the 1. Alcoa recommends the use of indicator tests such as the short rod test or the notch-yield ratio test (notch-tensile strength/tensile yield strength.475 plate is shown in Figure 20. the effect of the higher KIc values on design against fracture instability is quite significant. Since critical crack sizes are proportional to the square of the K 1 value. The specimen is loaded in a special mechanism designated as a "Fracjack"® by its manufacturer TerraTek.9 mm) specimen is used to test material equal to or greater than 1. For thin plate 0. "Standard Practice for R-Curve 4 . The current minimum acceptance values for K and the critical short rod and notch.250-0.4 mm) diameter specimen.ST_? Method 5545 "Standard Practice for ?lane-Strain Fracture Toughness Testing of Aluminum __lloys. The 0. and orientations." ASTM Method 3645 is used because in many cases for high strengthhigh toughness aluminum alloys. Such notch-yield ratio and K n relationships differ betwee alloys. Figure 22 illustrates the relationship of notchyield ratio with K 1 for both the 0.9 mm) diameter specimens. Alcoa will provide recommended procedures for the solution heat treatment and artificial aging of Alcoa produced 7475 sheet and plate. THERMAL TREATMENTS Alcoa has developed special thermal practices to optimize the strength and fracture toughness of 7475 sheet and plate products. • aiue and nominal material thickness-is shown in Figure 24. CORROSION CHARACT7RIqTTGS Atmospheric Weathering.250 inches (6. An example of the relationship between the K70. No toughness indicator relationships (short rod or notch-tensile) have been developed for plate in this thickness range. Pennsylvania industrial atmosphere and the Point Judith. center cracked panels. afoliation and Stress-Corrosion Cracking On a temper-for-temper basis. No failures have occurred during eight years exposure to these environments. FORMING RECOMMENDATIONS Suggested minimum bend radii for 7 4 75 sheet and plate products in the annealed and heat-treated tempers are shown in Table XIV. Panels machined to the T/10 plane from seven production lots of 7475-T7651 plate and sheet were exposed to seacoast and industrial environments for eight years with no evidence of exfoliation. transverse direction at stresses between 36-51 ksi(248-352 MPa). a single discrete point e y cluatibi=1." Me -7. Similar tests conducted on fifty-four production lots of 7075-T7351 resulted in no failures during eight years exposure at these two stations. In situations where forming may be required in the "0" and "W" condition. of 7475-T7351 plate at -65°F K . Because of the high loads associated with testing this type of specimen. An alternative way of determining the toughness of thin plate is to determine K values from 16 inch (406. it is recommended that the aaterial be alclad. exfoliation and stress-corrosion cracking is involved.4 c am) wide. Strength levels were only slightly lower than the T651 temper.Tetermination. Alcoa has conducted both exfoliation and stress-corrosion tests in all tempers of 7475 in accelerated and atmospheric environments.4 am). Tensile bar and C-ring specimens from twenty production lots were stressed in the short- The plane-strain fracture toughness. ID. Table XI. . f full material thickness Ihd a 5 inch (127 am) width. o C) according to tests of three lots is only 2 to 10 percent less than that at room temperature. the plates are generall y machined to a common thickness of 0. Rhode Island seacoast atmosphere. The T7651 temper of 7475 was developed to provide a high degree of resistance to exfoliation corrosion attack and improved resistance to stress-corrosion cracking. Stress-corrosion tests of short-transverse specimens from four production lots of 7475-T7651 plate stressed at 25 ksi (172 MPa) were exposed to the same environments for eight years with no failure. Requests for 7475 heat treating procedures should be directed to the nearest Alcoa sales office. 075. Additional testing may be required to quantify the average effect of low temperature on the toughness of high strength aluminum alloys. The T7351 temper of 7475 is recommended for optimum resistance to stress-corrosion cracking. Generally 7475 sheet and plate products have :31ightiv improved :orming characteristics over . depending on plate thickness and exposed to the Alcoa Center. For applications involving corrosive environments or where ood surface appearance is required.tn :rack:: rowth :esistance =rye (R-curve) feveloped from a test of a compact tention specimen f. the overall corrosion resistance of 7475 is essentially the same as that of 7075 where atmospheric weathering. Test results have shown that T761 temper sheet less than 0. If the conductivity is 41 percent IACS (International Annealed Copper Standard) or higher and mechanical properties meet specified minimum limits. or 2. The stress-corrosion cracking test described in specification ASTM G47 is recommended for evaluating the stresscorrosion cracking resistance of 7475. examined on the surface. the mechanical properties meet specified minimum limits. above. 3. Electrical conductivity along with y tensile ield strength has been shown to correlate with exfoliation and stresscorrosion resistance.5 mm) and over in nominal thickness (T) and T7651 plate. 6 .anodized and/or tainted. not fail by stress-corrosion will cracking. requirements of is acceptable. Material failing to meet requirements of paragraph 1.7. and the following rules for acceptability have been established: 7475-T7351 Plate 1. will not show exfoliation equal to or greater than that illustrated b y Photograph B.100 inch (2.1 mm) and over in nominal thickness will not fail by stresscorrosion cracking when stressed in the short-transverse direction to 25 ksi (172 MPa) in accordance with ASTM 047. c on completion of :Teets the above. If the conductivity is 39 percent IACS (International Annealed Copper Standard) or higher. (a) the conductivity is 39 percent or higher and the long-transverse yield strength exceeds the specified minimum b y more than 8 ksi (56 MPa) or. Alloy 7475 hand and die forgings have been made experimentally. Control Tests Required for tccentable Corrosion Performance The exfoliation corrosion Lest described in specification AST'_: G34-79 "Exfoliation Corrosion Susceptibilit y in ?XXX and 7XXX Series Aluminum Alloys (EXCO Test)" is recommended b y Alcoa Laboratories for evaluating the exfoliation corrosion resistance of 7475. which is stressed at 40-45 ksi (276-311 MPa) in the short-transverse direction in accordance with ASTM G4. 7475 forgings and extrusions have not been promoted commercially because other available 2. it is acceptable.5 mm) in nominal thickness. (b) the conductivity is less than 39 percent but at least 38 percent. and the long-transverse yield strength does not exceed the specified minimum value by more than 8 ksi (55 MPa).100 (2.1 mm) and over in nominal thickness. examined at a T/10 plane. Likewise T7651 plate 0. 2. 4. and T761 temper sheet 0. the sheet or plate is acceptable. The material is considered marginal and must be corrosion tested if. Plate found to be unacceptable may be fiven additional precipitation treatment and if such treatment. Figure 2 of ASTM G34-72. However. above or having a conductivity less than 38 percent is not acceptable. Material found unacceptable may be given additional precipitation heat treatment and if. Tests have shown that 7475-T7351 plate 0. the plate 475-T7651 Plate ana 7475-1761 Sheet _. 7475 FORGINGS AND EXTRUSIONS Alcoa is currently supplying extruded rod for the manufacture of 7475-T61 aluminum cartridge cases that require an optimum combination of strength and toughness.750 inch (19. hard coating and applying chemical conversion coatings to 7075 can be used satisfactoril y with 7475. or 2. the plate is acceptable. FINISHING The same techniques used for anodizing. upon competion of such treatment it meets requirements of paragraph 1.750 inch (19. Superpiasticit y refers to the ability of a material to reach very high. 7475 superplastically formed : arts co not :22 =2 :7. ADDITIONAL INFORMATION Requests for additional information should be discussed with an Alcoa sales engineer. general. . Alcoa is currently supplying 747502 temper sheet material to customers for their superplastic forming operations. toughness In or corrosion resistance required. This results in cost reductions by eliminating the total number of parts required in typical aircraft subassemblies or by reducing the number of forming operations. This combination of properties is particularly attractive for new high performance aircraft being designed to durability and damage tolerance criteria. After forming. high fracture toughness and good resistance to fatigue-crack propagation at high-stress intensities. wing skins.ovailable __em :s=sr iompinations cf p roperties aria :DSt more citable frr these products.-7: d for 7475 suterplastic formed parts hnless there is a toughness requirement. late products. the solution heat :rootin g hric aging prac:ices "__commended :37 7C75 sheet in specification nIL-14-6o8sF are recommend. parts are heat treated to 7475-T62 or T762 type tempers depending upon the strength. 7or :his reason. Alloy 7475 sheet and plate are currently being used in a number of commercial and military aircraft programs. Weight reductions are also possible because of the elimination of rivets and overlapping joints. Superplastic 7475 sheet can be formed into complex shapes in a minimum number of forming operations. spars and bulkheads where high fracture toughness is a design consideration. CONCLUSIONS AND RECOMMENDATIONS Alloy 7475 sheet and plate products provide a combination of high-strength.2 optimized :oughness associated 7475 sheet and :. 4 75 "UPERPLAST 7 CA= TORMABLE Alcoa commercialized has an '„l itrafine grain 7475 com p osition sheet product that exhibits superplastic forming characteristics when deformed at '_? 60°. neck free elongations under certain combinations of temperature and strain.F (515°C) and at strain rates below 10 -3 sec ._1107S EUCh and :ampers h:rrentiY . Alloy 7475 sheet and plate should be considered for aircraft structures such as fuselage skins. The nearest Alcoa sales office should be contacted for additional 'information or 7475 superplastically formable sheet. A fine equiaxed grain structure is one of the major characteristics required for superplasticity. T. Part II: Applications in Aluminum Alloy Quality Assurance of Fracture Toughness. S. Senz and E. "The Sharply Notched Cylindrical Tension Specimens for Screening Plane-Strain Fracture Toughness. G. Y. I . Nevada 1974 April 17-19. "Methodology for Evlaution of Fatigue Crack-Growth Resistance of Aluminum Alloys under Spectrum I. "Metal Progress. SAE Structures Structural Dynamics and Materials Conference. Hawthorne. New York. Kaufman.AIAA. J." G. Wang. Las Vegas. pp 413-430. 8. V. Alcoa. 1974 May 23. American Society for Testing and Materials 1973. "Selecting Aluminum Alloys to Resist Failure b y Fracture Mechanisms. General Dynamics. Scarich.4 August 1981. Nevada 1974 April 17-19. Wells. 3. R. 1973 April 1. 750 Third Ave. 15th. Contract No.. 1977 June. Bretz. New York 10017. Scarich. "Exploratory Development for Effort to Obtain Design Data on Structural Aluminum Alloys in Representative AFML Environments.." J. SAE Structures Structural Dynamics and Materials Conference. H. R. "Design o . 5. Presented at American Society of Mechanical Engineers Design Engineering Conference. April 1982. M. for Fatigue and Fracture Resistance). "Progress in Flaw Growth and Fracture Toughness Testing. 15th. G. "Fracture Mechanics Impact on Specifications and Supply. E. ASME. "Aluminum Association Position on Fracture Toughness Requirements and Quality Control Testing Interim Report. J. Loading. V. Fatigue Environmental Fatigue Crack Growth Rates and Corrosion Characteristics of High Toughness-Aluminum Alloy Forings. Bucci. Volume 4. f Aluminum Alloys for High Toughness and High Fatigue Strength." J." Telesman. Kohm. AIAA. Final Report for period 4 August 1980 . N00019-80-C-427. Final Report for period 1 October 1981 Contract No. California." R. 13. "Fracture Toughness and Microstructure of High Strength Aluminum Alloys. AGARD Conference Proceedings. Mechanical Properties. Chicago. 185 (Specialist Meeting on Alloy Design 11." AFML-TR-73-83." Aircraft TR-77-102. Fracture Toughness. H. "Investigation of Fatigue CrackGrowth Resistance of Aluminum Alloys under Spectrum Loading. 10." The Aluminum Association. Northrop Corp. 7. 6. McDonnell Douglas Corp. 12. 1976 January. Northrop Corporation. "New Alloys for Advanced Metallic Fighter-Wing Structure. ASTM Special Technical Publication 632." R. F. 1972. Northrop Corporation and P. 30 November 1982. 1977 May 11." R. "Material Selection and Evaluation for Advanced Metallic Aircraft Structures.REFERENCES 1. E. R. Spring Society of American Institute of Mining. J. E." J. No. "Crack Growth Resistance in PlaneStress Fracture Testing." ASTM STP 536. R. Shults. Meyer and D. ASME. Engineering Fracture Mechanics. pp 334-349." 1975 March. G. Metallurgical and Petroleum Engineers. McCabe. Kaufman. 4. and P. "Plane-Stress Fracture Toughness and Fatigue-Crack Propagation of Aluminum Alloy Wide Panels. Collis. Illinois." D. Las Vegas. 2. G.' Spuhler. presented at Metallurgical Meeting. F. 14. Bretz. Staley." R. Sheet and Plate. Bucci. Alcoa. 9. " R. Chanani. "Alcoa Short Rod Fracture Toughness Indicator Test. Cieslak. April 1983." Stanley J. 1985.N00019-81--C-0550. May 26. 15. Alcoa. . 10 . 06 max. L. Remainder TABLE II TYPICAL PHYSICAL PROPERTIES OF ALLOY 7475 Density 0.10 max.3 Melting Range 980-1175°F 527.331 0.33 11 .9-2.25 5.05 max. 0.388 m/m°C 23. 0. Total Aluminum 0.21-0.15 max.9-13. 20.40 max. 2.9 0.EIGHT 7475 Silicon iron Copper Manganese Magnesium Chromium Zinc Titanium Others. 1.30 max.101 lb/in3 2.2 24.635°C Specific Heat @212°F (100°C) (0. 0.!ABLE I C P0SITTON L - .0 0.795 g/cm3 Electrical Conductivity @ 68°F (20°C) -T651 Temper -T7651 Temper -T7351 Temper IACS 35 40 42 ml (ohms mm 2) .15 max.2 0.18-0.20 max.'1I `' OR ALLOYS . Remainder 7075 0.1 0.2-2. 0.12 max.1-2.06 max. 0.372 0.0) x 10 -6 Thermal Conductivity @ 77°F (25°C) -T651 Temper -T7651 Temper -T7351 Temper cal/[(sec cm 2 °C)/cm] 0.3 23.9 0.2-6. 1.i7 AND -27 Y '.05 max.2-1.23 Btu/(lb °F) 963 J/(kg C) Btu/[(hr ft 2 °F)/ft] 80 90 94 in/in/°F (12.6 0.35 5.1-6. 0.18-0.4 x 10-6 Average Coefficient of Thermal Expansion 68°-212°F (20-100°C) Poisson's Ratio 0.50 max. Each Others. 1. .. ' in •-• ..1 cn I-I ♦-i .n . 71 C. 4 o n . ..0 r :T.... . L. .C) 0 c•I 4 ...------.-.. ... ..--n In Ln N 44.-... C C' -.-7. c•-• ..1... .0 c•-• .--I E 1-I 0 Ill -S 4..-• .--.> i I ..11 Ill .--i 0 .-4 . 1 n n n n. 7 ..o I I CC co n -.. Cr. n n ..0 . 4 .. CO 0 .C 'LC..... ..‘. ....” .. 44N In L.. a) a) u-1 0 • ..--. CN . n 0 47 I Cel „--.. .--. 4..• 1----• 0 CI. 4. ..-A .. . G 7/ 0....... .g .-.4 .-.-.--i 0: cc) ..-._..-I I•-• N ‘. fl-. ----.c.0 n ..--.... -. 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"F A 11 3 .. 4C 3 gie-MT>.. Z ".C1 111-1MMM. -^ ul0 C 88Q 0O"0000 00 " 0006 OO •BOO rrrrr r r :R ti G 8 .+000 00" 000 p 00"H p -g ^ti0 r "^O ".._ mc4w ^c y ^ O-p 00 ID M^1yOG <^^ N = o °>^ Q rye .OiO Ii " r - N ^ g s^ 17 . u^ ^o u: v. .a.-^^O } ^^^ .i7 O e e . .. m°ir E ^^ ^ vim° r aro 9 - 292 ^g^ _ mom 89 Cl) m . 00 ^ u.f^i mO.mo o ^o I -- ^.r .g . ^ ^ n : . ice= n^". p 8 $ rn Q U ^u ^^ pp ^ .c .. o M _ ^^ ^ ^ gym ^. .. ..g .-1 v10g g 88 .og -o .x Ii ^79 y M t^ 1 a yc p7 -3 'o MM 8 y o^3 tic .^ 3 I •.-^ g "'og og o " .Q ei tl r ^vN...^ wcE W ~ E 'Kill G 9 O .y 0 00 G . ^n n v..y w ° M N s ti _ _ __ ^^ rvi^'i `..c .^ggg 00 "C .c .c .r 1f10 000 .. v.^O _ Q^^m^m Q Z U vJ on^ :c .moo . 3R" F n p - C .. 000 00"Oi000 •-I VIOOp pp . $ J e g r syi• U W ya m a 0 J w yp° y v ^ _ m^r•i m:^ ^ u mm ^p O.0 ggg .y 00 ^. _ . This product has mechanical properties intermediate between bare and two-side alclad 7475-T61 sheet. 18 . Alcoa is currently supplying alclad one-side sheet in 7475-T61 temper. Minimum mechanical properties will be provided on request.TABLE IX ALCOA 7475 SHEET AND PLATE SPECIFICATION COVERAGE Product Form Temper (1) Specification MIL-HDBK-5D COVERAGE Bare Sheet Alclad Sheet Bare Sheet Alclad Sheet Plate Plate Plate 7475-T61 (1) AMS 4084A AMS 4207 AMS 4085A AMS 4100 AMS 4090A * AMS 4089A * AMS 4202A * Approved Approved Approved Approval pending Approved Approved Approved 7475-T61 7475-T761 7475-T761 7475-T651 7475-T7651 7475-T7351 * Mechanical property revisions have been requested NOTE: 1. 0) 23 (25.8) 24 (26.3) 22 (24. ksi in.4)* (89. (MPa ^) 16 Inch (409•4 mm) x 44 Inch (1117.2) 26 (28.9) 20 (22.6) 28 (31.3) 50 (55.4) 22 (24. ksi in.4) 17 (18.063 inch (1.0)* K .7) 30 (33.4) 25 (28.3) 34 (37.0) 24 (26.7) 37 (40.0) 29 (32.4) 18 (19. (MPa J) Compact Tension Specimen (ASTM E399-74) ORIENTATION ALLOY PLATE 7475 T651 T7651 T7351 T651 T7651 T7351 T7651 T7451 T351 T851 T851 42 (46.8) 18 (19.9) 37 (40.0) 24 (26.7) 24 (26.TABLE X TYPICAL FRACTURE TOUGHNESS VALUES HIGH STRENGTH ALUMINUM SHEET AND PLATE PRODUCTS K .7) 41 (45.0) 26 (28.0) 31 (34.8) 18 (19.4) 120 (131.6 mm) Center Cracked Panel ORIENTATION ALLOY SHEET 7475 T61 T761 95 (104. These alloys/products do not have guaranteed minimum fracture toughness values.9) 88 (96.0) 29 (31.0) 33 (36.7) 110 (120. 19 .9) TEMPER L-T T-L 2024 7075 T3 T6 --- 124 81 (136.2) 29 (31.4) TEMPER L-T T-L S-L 7075** 7050 2024** 2124 * ** Based on limited Alcoa tests of 0.60 mm) thick sheet.6) 27 (29.0) 43 (47. 3 46.1 130.5) (50.063 (1.T.T.5 93.9 45.7) (49.3) (51.0) (124.6) 7 42.6) ( 86.T.063 (1.7) (149.9 44.9 135.9 123.063 (1.6 (143.071 (1.8 (46. -65 (-54) R.9 122.9 133.4 51.5 (58.9 40.T. -65 (-54) R.2 ( 59.0) (108.3) (44.2) R.9) (134.3) 10 5 20 .T.6) R.2) (110. -65 (-54) R.9) 36 36 16 26 26 16 (MPa KIc' ksi Compact Tension Specimen (ASTM E399-74) Testing Temperature o f ( ° C) Orientation L-T T-L % Reduction in Toughness from RT to o -65 F (-54C) Orientation L-T T-L Alloy PLATE 7475-T7351 Thickness in.2) (59.6 113.6) 0. -65 (-54) R.4) (150.9) (44. (mm) 2. -65 (-54) R.T.5) 3.4 78.0) (135.T.25 (57.2) 2.047 (1.2 54.9) (147. ksi Vin.T.4 mm) x 44 in.6) 0.T.8 (138.2) 0.6) 0.T.6) 0.8 48.6 mm) Center Cracked Panel T-L Orientation % Reduction in Toughness from RT to o o -65F (-54 C) 0.4) 0. -65 (-54) R. (MPa v71) 16 in.2) ( 90.2 136.063 (1.T. -65 (-54) 126.8) 33 7475-T761 0.7 40. -65 (-54) R.8 98.6) 81.063 (1.TABLE XI TYPICAL FRACTURE TOUGHNESS VALUES ROOM TEMPERATURE AND -65°F (-54°C) HIGH STRENGTH ALUMINUM SHEET AND PLATE PRODUCTS Alloy SHEET 2024-T3 Thickness in.T. (486.063 (1.7) 12% (increase) 7% (increase) 7075-T6 0.50 (63. -65 (-54) R.8) (56.2 ( 89. -65 (-54) R.2) 54.7 100.00 (76. (mm) Testing Temperature °F ( ° C) K . (1117.2 141.7) (155.5) (102.0) (53. -65 (-54) R.7) (122.2) (143.9 111.055 (1.6) 130. -65 (-54) 52.3 81. 18) 0.32) Alclad 0.32) - - 0.18) 0. (MPa /) (1) Sheet Thickness in.4 mm) wide by 44 in.040-0.18) 0. Notch tensile strength to be determined by tests of 3 in.20-6.8) Alclad 0.20-6. (117.18) 0. (406.125 (1.125 (1.4) 60.02-3.32) Alclad 0.0 (95.6 mm) center crack panels per Testing of Aluminum Alloys.32) 7475-T761 Bare 0.249 (3. Reference ASTM E338 "Standard Method of Sharp-Notch Tension Testing of High-Strength Sheet Materials.126-0.9) - 75.0 (95.125 (1.0 (65.20-6.126-0.02-3.126-0.0 (82.20-6.249 (3.94 Notes: 1.0 (82.32) - 1.20-6.32) - - - - - 87.18) 0. Long transverse." Notch yield ratio acceptance criteria are still tentative and may be modified.9) Bare 0.18) 0.6) 80.95(5) 100.040-0.(mm) Test Direction Long Longitudinal Transverse 60.05(5) - - 0.32) Orientation L-T T-L Sheet Thickness in.040-0. (76.0 (87. 21 .02-3.20-6.02-3. 4. 5.040-0.126-0.249 (3.126-0.9) 75." 2.040-0.9) Bare 0. Critical stress intensity factor K c determined by tests of 16 in.TABLE XII BARE AND ALCLAD 7475 SHEET FRACTURE TOUGHNESS ( K r ) MINIMA AND NOTCH YIELD RATIO ACCEPTANCE CRITERIA Minimum Fracture Toughness K c ksi Notch Yield Acceptance criteria(3) (Notch Tensile Strengt /Tensile Yield Strength)(2) 3 in.125 (1.02-3.125 (1.6) 80.040-0.040-0. These values are also subject to customer acceptance.0 (87.18) 0.126-0.20-6.02-3.249 (3.72 Alclad 0. 100% K test c ASTM Method B646-78 "Standard Practice for Fracture Toughness 3.0 (65.4) 60.32) 0.2 mm) wide edge notched tensile specimens.91(4) 0.02-3.126-0.0 (65.98 Alclad - 0.125 (1.249 (3.20-6.249 (3.0 (109.126-0.249 (3.9) 87.02-3.249 (3.125 (1.68 0.125 (1.(mm) 7475-T61 Bare 0.18) 0.040-0. 0 (36. (mm) 0.500-4. K 1 for plate.50 In.4-38.749 (6.4-101.50 in.3) 25.00 mm) and be full thickness for plate up to 2." The L-T and T-L spe cimens of the standard proportions shown in ASTM E399 shall have crack length of not less than 2. i.250-1. Insufficient specimen thickness. in.37 (8) 2.3) 30.5 mm) thick. Excess plasticity as indicated by the ratio of P IF exceeding 1.4-38.5 mm).0 (30.4-19.1 mm) and greater using notched round tensile specimens per ASTM E602 "Standard Method for Sharp Notch Tension Testing with Cylindrical Specimens.6 mm).999 (31. max Q Proposed short rod acceptance values.5 mm) thick.0 (44. (63.250 (31. in. 4.1) 1.250-1.0 30.1) (6) (6) (6) (6) Short Transvers -17651 0.8) 1. b. 2. W=5.8) 1.5) 40.7) (6)(7) (6) Short Rod Value 54. (63. (63.000 (50. These values are also subject to customer acceptance.8-50.500 (6. Plate in thicknesses greater than these are subject to inquiry.749 (6.0) 0.75 in.6) 1.00 in. Notch yield ratios are still tentative and may be modified.4-101.0 42.1-38.0 (6) 1.000 (6.250 (31.5 mm) with other dimensions per ASTM E399.e.000-4. For plate thickness above 2.8) (9) Plate Thicknesg ) Tentative Minimum NY Range for NYR' Test. K Ic .500 (63. L-T direction may be lot released by long transverse NYR values of 1.1-38. 9. fracture toughness minima and test method are subject to negotiation.0 (27. to be determined in accordance with ASTM E399.50 in. shall be evidence of acceptable fracture toughness: a.50 in.250-1.TABLE XIII 7475 PLATE FRACTURE TOUGHNESS ( K c) / MINIMA AND NOTCH YIELD RATIO ACCEPTANCE CRITERIA FRACTURE TOUGHNESS (K Ic MINIMA) NOTCH YIELD RATIO ACCEPTANCE CRITERIA (2) (3) Minimum Plate Thickness for Applicable Fracture Temper -7651 Plate Thicii I ss in.48 1.8) 1.37 1.4-19. ( mm) Longitudinal Transverse 0. (19.750-1.500 (6.0 (33.8) 33. Plane strain critical stress intensity.250 (31. ksi in. 7.250 (31.250 (31. 5. 3.0) 0.20 Notes: 1.0) 0.500 (19.1.250--0. For plate thickness 2. For plate thickness below those indicated." 6. "Plane Strain Fracture Toughness of Metallic Materials.8) Minimum Fracture Toughness.8-101.750-1.00 in.250-4. 22 .249 (7.8) 2.0 (33.500 (19. (mm) T-L L-T S-L 1.1) Toughness minima. Type of indicator test and minimum value for lot release to be negotiated. (127.5) (4) 0. Notch yield ratio determinations (NTS/TYS) will be made for plate thicknesses 0. 8.1) (6) (6) (6) (6) -17351 0.250-0. (6.0) 33.4-31. (MPa m) L-T T-L S-L 30.0) 28.250 (31. All K values obtained shall meet all validity requirements of ASTM E399 for K except that K values which are invalid for the following reasgns shall Q Ic be considered meaningful and if equal to or greater than the applicablevalues in Table XI. L-T and T-L compact specimens will have "B" thickness of 2.7) 1.30.0 (36.250-1.6) 1. (63. BLE IV SUGGESTED MINIMUM BEND RADII FOR A 90 0 COLD SEND 7475 SHEET AND PLATE (Bend radii for various thicknesses expressed in terms of `'.5 t 3.5 t 1.0 t 4.0 5.0 t t t t 1.0 t 4.0 t 4.325) -0 -T61 -T761 -0 -T761 1.5 t 1.500 (38.125 0. t) Alloy SHEET 1Bare 7475 Temper 0.5 t 3.0 4.0 t 1.0 4.5 t i 2.-sickness.100) 3. (mm) 0.794) (1.525) 2.0 t 3.175) (2.0 t 3. iin.0 t 1.5 t 2.249 (6.0 t 1.090 0. (mm) Bare 7475 -0 -T7351 -T7651 -T651 0.110 0.375 (9.0 t Alclad 7475 PLATE Plate Thickness. in.0 t 3.600) 0.5 t 1.0 t 3.063 (3.016) Sheet Thickness.286) (2.5 t 3.5 t 2.5 t 4.T.0 t - .040 (1. 10 3 ksi (6. '.. (mm/mm) COMPRESSIVE TANGENT MODULUS. 1_ —TENSION %-L.. 0.COMPRESSION 60 LT 50 400 300 40 30 200 20 L — LONGITUDINAL LT—LONG TRANSVERSE I0 100 0 0 4 6 8 10 12 STRAIN.— TENSION — COMPRESSION-7 500 70 44 4 Pr 0.001 in.80 LT i I .9X10 3 MPa) 2 0 14 TYPICAL STRESS—STRAIN AND COMPRESSIVE TANGENT—MODULUS CURVES FOR 7475-T61 SHEET Figure 1 ./in. LT L' 500 70 60 400 50 U) C i f a 300 w 40 U) w cc 99 L . 0.LONG TRANSVERSE 20 200 100 Li] 0 0 2 8 10 4 6 STRAIN. / in.LONGITUDINAL LT. (mm/mm) 12 0 14 TYPICAL TENSILE STRESS-STRAIN CURVES ( FULL RANGE) FOR 7475-T61 SHEET Figure 2 .90 TLT 80 .01 in. 001 IN/IN (mm/mm) COMPRESSIVE TANGENT MODULUS. 10 3 KSI (6. 0.9X10 3 MPa) TYPICAL STRESS-STRAIN AND COMPRESSIVE TANGENT-MODULUS CURVES FOR 7475-T76I SHEET Figure 3 6 .80 I LT-COMPRESSION-7 i 500 70 1 L-TENSION -4/41"Aggit . L L-COMPRESSION LT.TENSION LT _ 60 400 50 300 40 30 200 20 L-LONGITUD NAL LT-LONG TRANSVERSE I0 _ 100 0 0 2 4 6 8 10 12 0 14 STRAIN. 0.01 in. (mm/mm) 0 TYPICAL TENSILE STRESS — STRAIN CURVES (FULL RANGE) FOR 7475 — T761 SHEET Figure 4 27 ./in.^ 500 vj W cr I- Y 50 300 w 40 30 L — LONGITUDINAL — LT LONG TRANSVERSE 20 100 I0 0 0 2 4 6 8 10 12 14 STRAIN.20 D1s 80 LT L 70 LT 60 400 . 30 . (MPa) —400 —300 —200 —100 80 70 60 50 40 30 20 0 100 200 300 400 500 600 1. KSI UNNOTCHED.286 mm) AND 0.10 0 10 20 30 40 50 60 MINIMUM STRESS.090 (2.20 . KSI NOTCHED.50 . LONGITUDINAL AND LONG-TRANSVERSE SPECIMENS ALCLAD 7475-T61 & T761 SHEET 0. (MPa) —400 —300 —200-100 0 100 200 000 Li 00 500 600 60 50 40 30 20 1 0 0 .175 mm) inch THICK Figure 28 .125 (3.MINIMUM STRESS. K t =3 MODIFIED GOODMAN DIAGRAMS AXIAL-STRESS FATIGUE TESTS.0 500 400 300 c—t7 cn cr) 2 — 200 100 7<- 1 0 0 — 10 50-40-30-20-10 0 10 20 30 40 50 60 70 80 MINIMUM STRESS. Kt= MINIMUM STRESS.40 . LONGITUDINAL AND LONG-TRANSVERSE SPECIMENS BARE 7475-T61 c.175 mm) inch THICK -inure 29 .. T761 SHEET 0. 300 U. SCSI NOTCHED.090 (2.40 .125 (3. ( MPa) .00 — 3 00 —200 —.. = MINIMUM STRESS. K 3 MODIFIED GOODMAN DIAGRAMS AXIAL-STRESS FATIGUE TESTS.286 mm) AND 0. K^.r 400 w n 50 40 30 20 100 H- 300 2i f^ 5 J c 200 c < C 2 10 0 —50 —40 —30-20 —i 0 0 10 20 30 40 50 60 70 80 MINIMUM STRESS. KS! UNNOTCHED.MINIMUM STRESS. (MPa) —400 —300 —200 —100 0 I 100 200 300 400 500 600 80 70 60 Ci) 500 400 ( (ID w w F- 50 R=-1.+30 3 100 no 300 4 +00 500 600 600 80 I) C- m 70 60 500 cri . 30 200 20 100 IO — 50 . ^ j !.30--20--I0 0 10 20 30 40 50 60 70 80 MINIMUM STRESS.0 40 I CYCLES ^ ^ I0 4 %/ j '. MIONIM TJ 11111•11MOIBIMEMINIMI O O 'SS3ILLS wnwinfw O ..n i.r) C) Cr) 1/1/1 SIM /MEMilkoMMION atON CZ) „.1 < 0.. m .72-.1101===1 ARINNENIMIPIZIIMI/ IIMMI cc MIWINIV Mill W ' C-) Wmummiv ammg milimull 7=ENUnimmai w =WM "P)A11111111MIMIIIIII 'W ci3 I AWFAIII > .1.111 Ainiamm .11.a4_C) =Nem s l IM O O CC ril l.- 2d1A1 5 SS3E1S Wnvulxvw O 1. 7c immommom mo O C..vam .min= iiiim •im ismosi co E E mom =PENNINE milmomMIEMMIMENIEL .. . mim unImismim I 422•111111ME ANNE • <> I 4•6 o = w = F- O n11111MMIIIIIMEMIME n • 4 40411.r•mmummim ii imal11. Lc.. 1..•n•• 1.x.1.:26--Au• -: 1 I I LO I 4- M I— L CC AIIMNSIMIIIIINVAL l'iMIWAMNIIIMIIIMINIIIMIl < cc H MOMMINIMMIONIMMUMAIMENVIIIMII R nAMISMINIIMINIMMIN111..1. 0 hN cNi ( "37 < cr) CIC Ll1 u cc O q cc 1.4( Li_ O O a:1 <1. cr) momIIINNalm mill•i1.1101M111 AUMINMENNIMINII A=MO MMNIMMIMOMMIMINII mimI UMMNNIMimwmilliim...r) Q a oc:Dl` 2 O -J 2.1 ======mnimm._mw.. c7 —t 4 W a_ 11 < • • co 111 11= mesmosoimmasmwommi Tosit IMIIIMMINIOMINIMIMM•NE IMENIMIMINIMMIIIMMIMMINNININIMMENEW ILIMMININIMIMMIIIMMM=IMENIM rairmimmEmumr•wamommonalummummims n—n . ... N- C) c:/ Lc) C-D <=..M11•1111M. Z AZIWAR .1 CO C:) Z z0 LC) 7. Ir .1 ci) C Q N Lu a CD . .m.1 < ) cf) L1. a r •• -r c=... '2dw `SS HIS AJnumm T 4 v 'Q _ Y ' ^ Lo to c I r^ N ^. .n _' C ry !..N M ^7 _ J - ^p SI ^^ '-L 1 co W J V W U- .% O ^.I ' _: u15 "nWI M . 75 in.33.25 in.8 — Room temperature Moist (RH > 90%) air R= +0. (6. (19. IVI Pa 10 i 1 I 1 1 1 0-3 X4 tests 5 '4 0 1 0-4 10-6 (1) c) 10-5 ="- —1 7 i o-7 — 1 0-6 = L-T orientation co ' 10-7 1 x 1 X x )146 7475-T651 plate 0. in.3 mm) x = ! 10 .^ 2 K. Full Range Fatigue Crack Growth Rate Data 7475-T651 Plate Figure 9 .9 7 40 i o-- 10 1 0-9 1 1 5 ! ! I l i 10 ksi . f = 25 Hz -1 WOL specimen thickness = 0.05 mm) thick - 1 0-8 1 0. i ill.33.AK. ksi 10 40 Full Range Fatigue Crack Growth Rate Data 7475-T7651 Plate Various Specimen Orientations Figure 10 J3 .3 mm) I I I 10 -10 10 - 9 L 1 5 AK. 1111111 till 10 -8 co 0 10 -9 1 0 -8 n Room temperature Moist (RH > 90%) air R=+0.25 in.f=25 Hz CT specimen thickness = 0. (6. MPa i 7 vm 10 40 10 -5 `i 0 -3 j 5 7 1 0 -4 Specimen orientation q L-T (1 tes'' o T-L (1 tes 10-6 2 10-5 10 -7 E z z co 10 -7 I . MBA Pa 1 105 7 I 1 i 10 40 1 0-5 1 0 -4 o Specimen orientation L-T (2 tests. (6.3 mm) 10-9 10-1° 40 10-9 1 5 10 AK. (38.1 mm) thick 1 0-8 Room temperature Moist (RH > 90%) air R= +0. Full Range Fatigue Crack Growth Rate Data 7475-T7351 Plate Various Specimen Orientations Figure 11 24 . f = 10.33. WOL specimen) T-L (1 test.AK. CT specimen) 10-6 10-5 10-7 10-6 10-8 10-7 7475-T7351 plate 1.25 in. ksi On.25 Hz Specimen thickness = 0.5 in. ksi 1An. (6.05 mm) thick R = +0.25 in.3K.5 in.30 Hz Full thickness CT specimen 10.8 z —1 T-L orientation co 1 7475-T7351 plate 1 0-9 3. ksi Fatigue Crack Growth Rate Data 7475-T7351 Plate Various Test Environments and Plate Thicknesses Figure 12 35 . 10.9 mm) thick R = +0.m: a) 1 z 10-6 0 ° ^ _ 10-7 A U I- U E M 10-7 10-8 10.I 1 9 T-L orientation 7475-T7351 plate 0. (25. 10.33.0 in.9 1 1 5 ° ° 1 0. (19. MPa v m 10-3 10-4 a) 10-5 A U C 1 I i 5 I I 1 10 I 40 F - Environment Room temperature Dry (RH < 10%) air (1 test) Sump water (1 test) 1 0-5 . MPa vm 5 10 I I I i E nvironment Room temperature q Dry (RH < 10%) air (2 tests) o Sump water (2 tests) I i i i I 10-3 10-4 1 40 10-5 o ° 10-6 a) U E 10-7 0 10-6 z 10-7 10-8 10.3 mm). 30 Hz t — WOL specimen thickness 0. AK.75 in. (88.33.8 Z ca 1 O-9 10-10 40 5 10 AK. A — ° 1'[. 20 .4 mm) __ 10-10 10 40 3K. f = 2. f = 2. 1. 20. (2.. '. ..=-1 1 077 9 Alclad 7475-T61 sheet 0. _ _ Room temperature = 1 0. AK.. f= 13. f= 13.33. n' E. 0 1 0- k -= 10-8 L .6 1 0 -b 6.2 mm) thick R= +0. 1 AK.90 '.3 Hz Full thickness CCT specimen -A 10-10 L. _.:Salt fog (3 tests) : ii 11 1 0-5 1 06 10-7 014'9 ma 5 .10-8 A 1 0-7 Environment Room temperature 'Dry(RH < 10%) air (2 tests) I0-4 .088 in.125 in. ksi in.• 5 MPa M 10 .. 1 40 1 0-5 o-6 1 0-6 ar . = xMoist (RH . 1 10-8 . 1 1 0-3 • 10-4 371 0-5 U I I Environment Room temperature +Ambient air (5 tests) 1 40 J.33.125 in. 40 5 AK. 1 0 .33. ksi 10 in. iiiii I 1 0-8 o-9 11 5 AK. . : Salt fog (1 test) -4 --._.10 3 1 0-7 1 0-5 1 0-9 1 1 • 1 7475-T61 plate 0.) air (3 tests) . MPa rT1 5 10 I I 1 1 " 40 5 1 0 40 AK. (3. MPa rT1 5 10 I I I II..r 1 6 . K.eV .0•••• 5 0 1 0-5 1 0-6 - 8 10-7 S.0 T-L orientation L-T orientation 1 0-8 -3I --.33. (2.T orientation -1 7 L-T orientation Alclad 7475-161 sheet 0. (5_.. MPa 40 1 0-5 5 rii 1 0 40 Q9 :4 . ksi s in.. Specimen Orientations and Sheet Thicknesses Figure 13 36 . 40 Fatigue Crack Growth Rate Data Bare and Alclad 7475-T61 Sheet Various Test Environments. + 10 -5 1 0.--Ambient air (2 tests) 1 4 ..l.v.- 1 1 0-3 = 5 Envir Environment -'5 1 0. < o . .= = I R= +0. i:. 10-9 7. (3. ksi 10 in.3 Hz Full thickness CCT specimen I ! I I ( L-0 10 5 AK.24 mm) thick 1 0-9 10-10 != .100 in.2 mm) thick R = +0.3 Hz Full thickness CCT specimen ( I ti 0 L 7.6. 10-9 1 010-10 1 0-9 5 7475-161 sheet 0. . 1 -g -- - °1 .L 5 1 0-5 . = 13.L.74'.F . .'s' io.54 mm) thick +0._ Environment H Room temperature 1 0" (RH 1 05'4 air (1 test) • v Moist (RH • 90%) air 11 test). f= 13.3 Hz R Full thickness CCT specimen 1 i 1 1 0wH. -^ 10-7 05 I C `a•^a 1 0.3 Hz Full thickness CCT specimen 5 1 0 40 1 0- 8 ? 10 8 - 1 1 0-9 in -L orientatio n -1 1 0-7 E 7475-7761 sheet 0. (3. Fatigue Crack Growth Rate Data Bare and (7072) Alclad 7475-T761 Sheet Various Test Environments.m K.m pO '^'n ^Salt fog (1 :est) v R o ° 10-6 U T 0-5 ^ y h yb 1 0-7 1 0-6 -1 'SS-m T-L orientation 4 ° .33. (3.128 in.33• f 18. MPa.33.=Dry (RH < 10 %) air (1 test) -Moist (RH % 90°0) air (2 testsl.125 in.2 mm) thick R=+-0. ksi . m 1 0 40 1 0-3 Environment 1 0-4 Room temperature Dry (RH < 10`) air (1 test) -Moist (RH .3 Hz 1 0-9 108 1 0-9 106 1 0-10 Full thickness CCT specimen = 10-10 1 0 -9 1 I I I I 5 10 40 AK. ^ < - z 1 1 07 ^ L-T orientation 7475-7761 sheet 0.)= 13. MPa m 5 1 0 -3 e Environment 1 0 40 1 0-3 1 5 En vironment Room temperature 1 0-5 1 0-4 10-5 Room temperature q Dry (RH < 10':) air (1 test) x Moist (RH > 90':) air (1 test) o Salt fog (1 test) 1 0-4 10-6 0 U 1 oo .f=13..f=2. 20 Hz 10-10 40 5 10 AK. Specimen Orientations and Sheet Thicknesses Figure 14 37 . K.7 U U E v 1 0-6 . in..125 in.33.. ksi . 5K. in.' p°^ °° e a 10-5 . ksi 10 40 E 10-8 Z in c 1 0 -6 z 1 Z 10-7 1 10-9 ^I m 10_ 7 is E 1 0-8 T-L orientation _ (7072) Alclad 7475-7761 sheet 0.90%) air (3 test s`'ii Salt fog t3 tests) r 10-5 F 106 .965 mm) thick R = +0.1 0-6 ^. in. (0. ksi .. (3. 40 1 0-3 1 Q5 MPa 5 10 ' 5 . MPa ( 1 0 40 1 0-5 ° 1 .25 mm) thick 1 0-6 1 0-9 1 0-8 10-9 1 0-10 Full thickness CCT specimen 10-9 1 1 1 1 1 1 1 1 ) 1 1 I R=+0.7072) Alclad 7475-T761 sheet 0. K.038 in.2 mm) thick R=-0.90 : -) air (1 test) ° °^ :Salt fog (1 test) t ! ° 1 0-6 y rEnwonmen omtemperature y (RH < 10%) air (3 tests) 10-4 <Moist (RH '. _K. 20 Hz Full thickness CCT specimen 1 5 AK.3. Representative portions of stress history of each spectrum 0 Tension-compression spectrum (Fighter horizontal tail hinge) Fatigue Crack Growth Rate Spectrum Ranking (References 13 and 1 4) Figure 15 38 .24 in.000 E tq 5.) - Tension-dominated spectrum (fighter wing root) U) 0 —100 1 00 E 0 a) a) c. 20.GA 13002 3 25. Spectrum life for crack growth from 0.000 k- Tension dominated spectrum -"" (Fighter wing root) 1-7 Tension-compression spectrum (Fi g hter horizontal tail) (Average of two duplicate tests) O 1 5.000 0 2024T351 74751651 7475T7351 705017451 707517351 707 T651 A.000 p-or.) a.15 a) a) 4. (6 mm) to failure at a maximum peak stress of 21 ksi (145 MPa) g 100 E .) 10.000 I- 0.6‘ a) c. —100 B. y '---' -••.l _ ^-' CO = Hi 0r' r ^` Q W W y r F.^ -I T ^'4k3 rr i ail..rd LU r _ p .T T J ___i= T t T W J' 77 z W C . + . _ z a}â 1^. 27 Thickness.27 2. (in. (mm) Thickness.10 0.) 7475-T761 0. x 33 in.81 5.08 6. O8 0 88 40 L -T Direction 44 44 T-L Direction 0 0. (mm) 2.10 0.00 0.81 5. (in.27 I Thickness.05 0.08 I I 6.35 1. (406 x 1117 mm) Center Crack Panels Figure 17 40 .25 Thickness.81 2.54 3.35 160 • 1 20 Invalid per ASTM E561 • 8 0 • • 176 160 0 2.20 0.08 6.15 0.15 0.n Alclad 40 .05 Thickness.1.35 1.15 0.) Bare 7475-T61 Thickness.00 0. ( mm) 1.54 3.05 0.00 0.10 0.05 0.15 0.) Bare 7475-T61 0.) 7475-7761 0.25 0.10 0.08 6.54 3.25 0.35 160 176 160 176 - 1 20 O o 0 80 - 8C18 a 0 8 1O 132 a_ q 132 2 88 Ne' 40 k 0. cP n• T-L Direction qq 132 l'!" q q q1 OE 88 • 2 80 L-T Direction 88 NZ 80 CI Bare .81 5.54 5.20 Thickness.120 176 • • $ 132 12 a.25 Critical Stress Intensity Factor (1(c) Bare and Alclad 7475 Sheet 16 in.27 2.1 . (in.20 Thickness. (mm) 3.20 0.00 0. (in.0 Bare Alclad • 44 40 44 0 0. ---j 7 160 Ls — .6) 1.4 (35. T761 TEMPERS 0..063 in..1 mm) WIDE CLWL SPECIMEN ( WANG) 7475-T761 TEMPER 0.1 mm) WIDE CLWL SPECIMEN (HEYER AND McCABE) 20 7075-T6 TEMPER 0.0 (25.1) 0.5 mm) WIDE CLWL SPECIMEN 40 SPECIMEN TYPE CLWL . O a CRACK RESISTANCE CURVES FOR 7475 SHEET Figure 18 41 . (1. (1.063 in..4) 1.6 mmi THICK T-L ORIENTATION 36 AND 120 in. (1.8 (in. 80 60 7475-T761 TEMPER 0.6 mm) THICK T-L ORIENTATION 10.4 AND 3048 mmi WIDE CLWL SPECIMEN 240 220 200 180 IC > cn 160 140 z 120 100 LU .240 260 220 200 (HEYER AND McCABE) 7475-T61.) ( 45.-.. (914.063 in. (259.- --- 1 40 120 cz / cc \ (.. (2. T761 TEMPERS U C-.7) (mm) CRACK EXTENSION.1 in.4 mm) WIDE CCT SPECIMEN 100 80 60 0.2) 1. (259.2 in. ^.6 mm) THICK T-L ORIENTATION 5..2 (5.6 (15.6 mm) THICK L-T AND T-L ORIENTATION 16 in. (129.- I— 00• / ---.CRACK LINE WEDGE LOADED CCT .CENTER CRACK TENSION 20 + 0 ' 0 0.4LCOA) (HEYER AND McCABE) 7475-T761. 7 / O ..3 mm) THICK T-L ORIENTATION 10. .091 in. (1..2 in. (406.063 in. 6 mm) 120 • • • • • • • • 132 K c specimen l 110 . (1.17 Tensile yield strength.0-6.040-0. Fracture toughness not guaranteed for these alloys. 7075-T6.249 In. 2014-T6 7178-T6 • 2024-T86 66 • 44 20 0 22 0 7475-T61 A 7475-T761 20 30 40 50 60 70 80 90 Tensile yield strength.4 mm) I 140 4" 154 44" (1117. Tensile Yield Strength 0. 0 6061-T6 •0 40 Note: Limited Kc data on 2024-T3. 6061-T6. MPa 207 276 345 414 483 552 1 • • • • • • • • 16" (406. ksi (Long transverse direction) Critical Stress-Intensity Factor K c vs.: 2024-T3 • • 88 ct.GA 18002.3 mm) Thick Sheet Figure 19 42 . STRAIN STRESS-INTENSITY FACTOR KI D . MPa 70 an snn 70 50 COMPACT . vs YIELD STRENGTH 7475 PLATE 1 TO 3.TENSION SPECIMEN 60 50 L1 40 Y 30 000 40 cz 30 20 1415 NLAIt 20 O 1651 q 17651 A 17351 10 10 T-L ORIENTATION 0 50 60 70 80 0 TENSILE YIELD STRENGTH.GA 18002.2 TENSILE YIELD STRENGTH.5 inch (25.4-88.9 mm) THICK Figure 20 43 . ksi PLANE . 81 thru 5.18 1 98 160 — 0 176 140 — 1 54 120 — c 132 2 • Y.92 mm) Figure 21 44 .9 1 1.233 In.8 I 0.150 thru 0.3 inch wide edge-notch specimen Fracture Toughness. (3.0.7 I 0.180 GA 18002. Notch-Yield Ratio (L) Bare 7475-T61 Sheet .0 44 NYR (L) .6 I 0.) 100 — 110 3 80 — 88 60 — 66 40 0. K c (L-T) vs.5 I 0. 60 1.0.8 48.(dia.8 A 1. in. (25 thru 101.4 24 1.6 mm) Figure 22 45 .45 1.50 1. (12.25 1.6 35.6 n 57.65 NYR (LT) .0 7E 36 32 28 Notch diameter 39.2 52.500 in.060 in. (26.984 thru 4.30 1.35 1. as noted) Fracture Toughness. Notch-Yield Ratio (Long Transverse) 7475-T7351 Plate .7 mm) 30.9 mm) I 1-_I 26.L) vs.2 q 0. K 1C (T.55 1.4 44. 56 52 48 J 44 40 N GA 18002.20 1.19 61.40 1.000. 60 66. . Short Rod Value for 7475-T7351 Plate (L-T.0 ill 35 38. i co 30 33. T-L & S-L Orientation) Figure 23 .0 12. U 45 49.5 75 Fracture Toughness vs.0 =al n 40 0 a) h.5 CY) C a) 44.5 2..5 50 U (r) a) E 55.! 25 30 35 40 45 60 65 Short rod value (SR4) 50 55 70 27.0 55 60. E r O C) to E Z C T O C E cr O 0z N O N r 0 Q Cl) J9 0 r 0 N r • C 0 0 r 0 co 0 (0 0 ql O O N 0 CS ui is} i sualui ssa.edW sza)i C m Cl) w N M r 0 r r co co CO co q* It Cl) Cl) 0) Y'+ V 00 E r c_ I- 0) Eu? vt M Cl) M ^ r II C N 04 HN J ^ O C Y ^ ttj C7 V 00 C V_ L N L '^ M O 't O N N O rr T ' a^ ow E .q s Cc 47 .