CHAPTER 4 MAGNESIUM ALLOYS 4.1 GENERAL. MMPDS January 2003

Transcription

1 CHAPTER 4 MAGNESIUM ALLOYS 4.1 GENERAL This chapter contains the engineering properties and characteristics of wrought and cast magnesium alloys used in aircraft and missile applications. Magnesium is a lightweight structural metal that can be strengthened greatly by alloying, and in some cases by heat treatment or cold work or by both ALLOY INDEX The magnesium alloys in this chapter are listed in alphanumeric sequence in each of two parts, the first one being wrought forms of magnesium and the second cast forms. These sections and the alloys covered under each are shown in Table 4.1. Table 4.1. Magnesium Alloys Index Section Designation Magnesium-Wrought Alloys AZ31B AZ61A ZK60A Magnesium-Cast Alloys AM100A AZ91C/AZ91E AZ92A EZ33A QE22A ZE41A MATERIAL PROPERTIES Mechanical Properties The mechanical properties are given either as design values or for information purposes. The tensile strength (F tu ), tensile yield strength (F ty ), elongation (e), and sometimes the compressive yield strength (F cy ) are guaranteed by procurement specifications. The properties obtained reflect the location of sample, type of test specimen and method of testing required by the product specification. The remaining design values are derived values; that is, sufficient tests have been made to ascertain that if a given material meets the requirements of the product specification, the material will have the compression (F cy ), shear (F su ) and bearing (F bru and F bry ) strengths listed Tension Testing Room-temperature tension tests are made according to ASTM E 8. The yield strength (F ty ) is obtained by the offset method using an offset of 0.2 percent. The speed of testing for room-temperature tests has a small effect on the strength and elongation values obtained on most magnesium alloys. The rate of stressing generally specified to the yield strength is less than 100,000 psi per minute and the rate of straining from the yield strength to fracture is less than 0.5 in./in./min. It can be 4-1

2 expected that the speed of testing used for room-temperature tension tests will approach the maximum permitted. Elevated-temperature tension tests are made according to ASTM E 21. The speed of testing has a considerable effect on the results obtained and no one standard rate of straining is given in ASTM E 21. The strain rates most commonly used on magnesium are in./in./min. to the yield and 0.10 in./in./min. from yield to fracture [see References (a) to (d)] Compression Testing Compression test methods used for magnesium are specified in ASTM E 9. The values given for the compressive yield strength (F cy ), are taken at an offset of 0.2 percent. References (a) and (b) provide information on test techniques Bearing Testing Bearing tests of magnesium alloys are made according to ASTM E 238. The size of pin used has a significant effect on the values obtained, especially the bearing ultimate strength (F bru ). On tests made to obtain the data on magnesium alloys shown in this document, pin diameters of and inch were used. For pin diameters significantly larger than inch lower values may be obtained. Additional information on bearing testing is given in References (a) and (b). Bearing values in the property tables are considered to be dry pin values in accordance with the discussion in Section Shear Testing The shear strength values used in this document were obtained by the double shear method using a pin-type specimen, the punch shear method and the tension shear method as applicable. Just as tensile ultimate strength (F tu ) values vary with location and direction of sample in relation to the method of fabrication, the shear strength (F su ) may be expected to reflect the effect of orientation, either as a function of the sampling or the maximum stresses imposed by the method of test. Information on shear testing is given in Reference Stress Raisers The effect of notches, holes, and stress raisers on the static properties of magnesium alloys is described in References (a) through (c). Additional data on the strength properties of magnesium alloys are presented in References (d) through (h) Creep Some creep data on magnesium alloys are summarized in Reference Fatigue Room-temperature axial load fatigue data for several magnesium alloys are presented in appropriate alloy sections. References (a) and (b) provide additional data on fatigue of magnesium alloys PHYSICAL PROPERTIES Selected experimental data from the literature were used in determining values for physical properties. In other cases, enough information was available to calculate the constants. Estimated values of some of the remaining constants were also included. Estimated values are noted ENVIRONMENTAL CONSIDERATIONS Corrosion protection must be considered for all magnesium applications. Protection can be provided by anodic films, chemical conversion coatings, paint systems, platings, or a combination of these methods. Proper drainage must be provided to prevent entrapment of water or other fluids. Dissimilar metal joints must be properly and completely insulated, including barrier strips and sealants. Strain-hardened or age-hardened alloys may be annealed or overaged by prolonged exposure to elevated temperatures, with a resulting decrease in strength. Maximum recommended temperatures for prolonged service are reported, where available, for specific alloys. 4-2

3 4.1.5 ALLOY AND TEMPER DESIGNATIONS Standard ASTM nomenclature is used for the alloys listed. Temper designations are given in ASTM B 296. A summary of the temper designations is given in Table Table Temper Designation System for Magnesium Alloys a Basis of Codification The designations for temper are used for all forms of magnesium and magnesium alloy products except ingots and are based on the sequence of basic treatments used to produce the various tempers. The temper designation follows the alloy designation, the two being separated by a dash. Basic temper designations consist of letters. Subdivisions of the basic tempers, where required, are indicated by a digit or digits following the letter. These designate specific sequences of basic treatments, but only operations recognized as significantly influencing the characteristics of the product are indicated. Should some other variation of the same sequence of basic operations be applied to the same alloy, resulting in different characteristics, then additional digits are added to the designation. NOTE In material specifications containing reference to two or more tempers of the same alloy which result in identical mechanical properties, the distinction between the tempers should be covered in suitable explanatory notes. Basic Temper Designations F As Fabricated. Applies to the products that acquire some temper from shaping processes not having special control over the amount of strain-hardening or thermal treatment. O H Annealed Recrystallized (wrought products only). Applies to the softest temper of wrought products. Strain-Hardened (wrought products only). Applies to products that have their strength increased by strain-hardening with or without supplementary thermal treatments to produce partial softening. The H is always followed by two or more digits. H1 H2 H3 Strain-Hardened Only. Applies to products that are strain-hardened to obtain the desired mechanical properties without supplementary thermal treatment. The number following this designation indicates the degree of strain-hardening. Strain-Hardened and Then Partially Annealed. Applies to products which are strain-hardened more than the desired final amount and then reduced in strength to the desired final amount by partial annealing. The number following this designation indicates the degree of strain-hardening remaining after the product has been partially annealed. Strain-Hardened and Stabilized. Applies to products that are strain-hardened and then stabilized by a low temperature heating to slightly lower their strength and increase ductility. This designation applies only to alloys which, unless stabilized, gradually age soften at room temperature. The number following this designation indicates the degree of strain-hardening remaining after the product has been strain-hardened a specific amount and then stabilized. Subdivisions of the H1", H2" and H3" Tempers: The digit following the designations H1", H2", and H3" indicates the final degree of strain hardening. Tempers between 0 (annealed) and 8 (full hard) are designated by numerals 1 through 7. Material having a strength about midway between that of the 0 temper and that of the 8 temper is designated by the numeral 4 (half hard); between 0 and 4 by the numeral 2 (quarter hard); between 4 and 8 by the numeral 6 (three-quarter a From ASTM B

4 Table Temper Designation System for Magnesium Alloys (Continued) a hard), etc. The third digit, when used, indicates a variation of a two-digit H temper. It is used when the degree of control of temper or the mechanical properties are different from but close to those for the two-digit H temper to which it is added. Numerals 1 through 9 may be arbitrarily assigned as the third digit for an alloy and product to indicate a specific degree of control of temper or special mechanical property limits. W T Solution Heat-Treated. An unstable temper applicable only to alloys which spontaneously age at room temperature after solution heat-treatment. This designation is specific only when the period of natural aging is indicated: for example, W ½ hr. Thermally Treated to Product Stable Tempers Other Than F, O, or H. Applies to products which are thermally treated, with or without supplementary strain-hardening, to product stable tempers. The T is always followed by one or more digits. Numerals 1 through 10 have been assigned to indicate specific sequences of basic treatments, as follows. T1 T3 T4 T5 T6 T7 T8 T9 Cooled from an Elevated Temperature Shaping Process and Naturally Aged to a Substantially Stable Condition. Applies to products for which the rate of cooling from an elevated temperature shaping process, such as casting or extrusion, is such that their strength is increased by room temperature aging. Solution Heat-treated and Then Cold Worked. Applies to products that are cold worked to improve strength, or in which the effect of cold work in flattening and straightening is recognized in applicable mechanical properties. Solution Heat-treated and Naturally Aged to a Substantially Stable Condition. Applies to products that are not cold worked after solution heat-treatment, or in which the effect of cold work in flattening or straightening may not be recognized in applicable mechanical properties. Cooled from an Elevated-Temperature Shaping Process and Then Artificially Aged. Applies to products which are cooled from an elevated-temperature shaping process, such as casting or extrusion, and then artificially aged to improve mechanical properties or dimensional stability or both. Solution Heat-treated and Then Artificially Aged. Applies to products that are not cold worked after solution heat-treatment, or in which the effect of cold work is flattening or straightening may not be recognized in applicable mechanical properties. Solution Heat-treated and Then Stabilized. Applies to products that are stabilized to carry them beyond the point of maximum strength to provide control of some special characteristics. Solution Heat-treated, Cold Worked, and Then Artificially Aged. Applies to products which are cold worked to improve strength, or in which the effect of cold work in flattening or straightening is recognized in applicable mechanical properties. Solution Heat-treated, Artificially Aged, and Then Cold Worked. Applies to products that are cold worked to improve strength. a From ASTM B

5 Table Temper Designation System for Magnesium Alloys (Continued) a T10 Cooled from an Elevated Temperature Shaping Process, Artificially Aged, and Then Cold Worked. Applies to products which are artificially aged after cooling from an elevated temperature shaping process, such as extrusion, and then cold worked to further improve strength. A period of natural aging at room temperature may occur between or after the operations listed for tempers T3 through T10. Control of this period is exercised when it is metallurgically important. Additional digits, may be added to designations T1 through T10 to indicate a variation in treatment that significantly alters the characteristics of the product. a From ASTM B JOINING METHODS Most magnesium alloys may be welded; refer to Comments and Properties in individual alloy sections. Adhesive bonding and brazing may be used to join magnesium to itself or other alloys. All types of mechanical fasteners may be used to join magnesium. Refer to Section when using mechanical fasteners or joining of dissimilar materials with magnesium alloys. 4-5

6 4.2 MAGNESIUM-WROUGHT ALLOYS AZ31B Comments and Properties AZ31B is a wrought magnesium-base alloy containing aluminum and zinc. It is available in the form of sheet, plate, extruded sections, forgings, and tubes. AZ31B has good room-temperature strength and ductility and is used primarily for applications where the temperature does not exceed 300EF. Increased strength is obtained in the sheet and plate form by strain hardening with a subsequent partial anneal (H24 and H26 temper). No treatments are available for increasing the strength of this alloy after fabrication. Forming of AZ31B must be done at elevated temperatures if small radii or deep draws are required. If the temperatures used are too high or the times too great, H24 and H26 temper material will be softened. This alloy is readily welded but must be stress relieved after welding to prevent stress corrosion cracking. Material specifications covering AZ31B wrought products are given in Table (a). Roomtemperature mechanical and physical properties are shown in Tables (b) through (d). The effect of temperature on physical properties is shown in Figure Table (a). Material Specifications for AZ31B Magnesium Alloy Specification AMS 4375 AMS 4376 AMS 4377 ASTM B 107 ASTM B 91 Form Sheet and plate Plate Sheet and plate Extrusion Forging The temper index for AZ31B is as follows: Section Temper O H H F AZ31B-O Temper Effect of temperature on the tensile modulus of sheet and plate is presented in Figure Typical room-temperature stress-strain and tangent-modulus curves are presented in Figure AZ31B-H24 Temper Effect of temperature on the mechanical properties of sheet and plate is shown in Figures through , and Typical room-temperature tension and compression stress-strain and tangent-modulus curves for sheet are shown in Figure AZ31B-H26 Temper AZ31B-F Temper Figures (a) and (b) contain fatigue data for forged disk at room temperature. 4-6

7 Table (b). Design Mechanical and Physical Properties of AZ31B Magnesium Alloy Sheet and Plate Specification. AMS 4375 AMS 4377 Form.. Sheet Plate Sheet Plate Temper 0 H24 Thickness, in Basis.. S S S S S S S S S S S S Mechanical Properties: F tu, ksi: L LT F ty, ksi: L LT F cy, ksi: L LT a. F su, ksi F b bru, ksi: (e/d = 1.5) (e/d = 2.0) F b bry, ksi: (e/d = 1.5) (e/d = 2.0) e, percent L E, 10 3 ksi 6.5 E c, 10 3 ksi G, 10 3 ksi 2.4 µ 0.35 Physical Properties: ω, lb/in C, K, and α. See Figure a F cy (LT) allowables are equal to or greater than F cy (L) allowables. b Bearing values are dry pin values per Section

8 Table (c). Design Mechanical and Physical Properties of AZ31B Magnesium Alloy Plate Specification. AMS 4376 Form.. Plate Temper H26 Thickness, in Basis.. S S S S S S S Mechanical Properties: F tu, ksi: L LT F ty, ksi: L LT F cy, ksi: L LT a.. F su, ksi F b bru, ksi: (e/d = 1.5) (e/d = 2.0) F b bry, ksi: (e/d = 1.5) (e/d = 2.0) e, percent: L E, 10 3 ksi 6.5 E c, 10 3 ksi G, 10 3 ksi 2.4 µ 0.35 Physical Properties: ω, lb/in C, K, and α. See Figure a F cy (LT) allowables are equal to or greater than F cy (L) values. b Bearing values are "dry pin" values per Section

9 Table (d). Design Mechanical and Physical Properties of AZ31B Magnesium Alloy Extrusion and Forging Specification. ASTM B 107 ASTM B 91 Form.. Extruded bar, rod, and solid shapes Extruded hollow shapes F Extruded tube Forging Temper Thickness, in.. # All b b Basis.. S S S S S S S S Mechanical Properties: F tu, ksi: L LT. F ty, ksi: L LT. F cy, ksi: L LT. F su, ksi F b bru, ksi: (e/d = 1.5) (e/d = 2.0) F b bry, ksi: (e/d = 1.5) (e/d = 2.0) e, percent: L E, 10 3 ksi 6.5 E c, 10 3 ksi G, 10 3 ksi 2.4 µ 0.35 Physical Properties: ω, lb/in C, K, and α. See Figure a Wall thickness for tube; for outside diameter # inches. b Bearing values are dry pin values per Section

10 α - Between 70 F and indicated temperature K - At indicated temperature C - At indicated temperature α α, 10-6 in./in./ F C, Btu/ (lb)( F) C K, Btu/ [ (hr)(ft 2 )( F)/ft] K, O & H Temperature, F Figure Effect of temperature on the physical properties of AZ31B. 4-10

11 Figure Effect of temperature on the tensile modulus (E) of AZ31B-O sheet and plate. 25 Tension 20 Compression 15 Stress, ksi 10 5 Ramberg - Osgood n (L-tension) = 12 n (L-comp.) = 30 TYPICAL Strain, in./in. Compressive Tangent Modulus, 10 3 ksi Figure Typical tensile and compressive stress-strain and compressive tangent-modulus curves for AZ31B-O sheet and plate at room temperature. 4-11

12 Figure Effect of temperature on the tensile ultimate strength (F tu ) and the tensile yield strength (F ty ) of AZ31B-H24 sheet and plate. 4-12

13 Figure Effect of temperature on the compressive yield strength (F cy ) and the shear ultimate strength (F su ) of AZ31B-H24 sheet and plate. Figure Effect of temperature on the bearing ultimate strength (F bru ) and the bearing yield strength (F bry ) of AZ31B-H24 sheet and plate. 4-13

14 Figure Effect of temperature on the tensile modulus (E) of AZ31B-H24 sheet and plate Tension Stress, ksi 20 Compression 10 Ramberg - Osgood n (tension) = 4.3 n (comp.) = 15 TYPICAL Strain, in./in. Compressive Tangent Modulus, 10 3 ksi Figure Typical tensile and compressive stress-strain and compressive tangent-modulus curves for AZ31B-H24 sheet at room temperature. 4-14

15 Figure (a). Best-fit S/N curves for unnotched AZ31B-F magnesium alloy forged disk, transverse direction. Correlative Information for Figure (a) Product Form: Forged disk, 1 inch thick Properties: TUS, ksi TYS, ksi Temp.,EF RT Specimen Details: Unnotched 0.75 inch gross diameter 0.30 inch net diameter Surface Condition: Polished sequentially with No. 320 aluminum oxide cloth, No. 0, 00, and 000 emery paper and finally No. 600 aluminum oxide powder in water References: Test Parameters: Loading - Axial Frequency cpm Temperature - RT Environment - Air No. of Heats/Lots: 1 Equivalent Stress Equation: For R values between -1.0 and Log N f = log (S eq -12.9) S eq = S max (1-R) 0.56 Std. Error of Estimate, Log (Life) = Standard Deviation, Log (Life) = R 2 = 55.2% For R values between 0.0 and 0.50 Log N f = log (S eq -15.0) S eq = S max (1-R) 0.33 Std. Error of Estimate, Log (Life) = Standard Deviation, Log (Life )= R 2 = 33.2% Sample Size = 194 [Caution: The equivalent stress model may provide unrealistic life predictions for stress ratios beyond those represented above.] 4-15

16 Figure (b). Best-fit S/N curves for notched, K t = 3.3, AZ31B-F magnesium alloy forged disk, transverse direction. Correlative Information for Figure (b) Product Form: Forged disk, 1 inch thick Properties: TUS, ksi TYS, ksi Temp.,EF RT Specimen Details: Notched, K t = inch gross diameter inch net diameter inch root radius, r 60E flank angle, ω Reference: Test Parameters: Loading - Axial Frequency cpm Temperature - RT Environment - Air No. of Heats/Lots: 1 Maximum Stress Equation: Log N f = log (S max ) Std. Error of Estimate, Log (Life) = Standard Deviation, Log (Life) = R 2 = 43% Sample Size =

17 4.2.2 AZ61A Comments and Properties AZ61A is a wrought magnesium-base alloy containing aluminum and zinc. It is available in the form of extruded sections, tubes, and forgings in the as-fabricated (F) temper. AZ61A is much like AZ31B in general characteristics. The increased aluminum content increases the strength and decreases the ductility slightly. Severe forming must be done at elevated temperatures. This alloy is readily welded but must be stress relieved after welding to prevent stress corrosion cracking. Material specifications covering AZ61A are given in Table (a). Room-temperature mechanical and physical properties are shown in Table (b). Table (a). Material Specifications for AZ61A Magnesium Alloy Specification Form AMS 4350 ASTM B 91 Extrusion Forging 4-17

18 Table (b). Design Mechanical and Physical Properties of AZ61A Magnesium Alloy Extrusion and Forging Specification.. AMS 4350 ASTM B 91 Form Temper. Thickness, in... #0.249 Extruded bar, rod, and solid shapes Extruded hollow shapes F a All Extruded tube Forging b Basis S S S S S S Mechanical Properties: F tu, ksi: L LT.. F ty, ksi: L LT.. F cy, ksi: L LT.. F su, ksi F c bru, ksi: (e/d = 1.5) (e/d = 2.0) F c bry, ksi: (e/d = 1.5) (e/d = 2.0) e, percent: L E, 10 3 ksi. 6.3 E c, 10 3 ksi 6.3 G, 10 3 ksi. 2.4 µ Physical Properties: ω, lb/in C, Btu/(lb)(EF) (at 78EF) d K, Btu/[(hr)(ft 2 )(EF)/ft] 46 (212 to 572EF) α, 10-6 in./in./ef.. 14 (65 to 212EF) a For cross-sectional area #25 square inches. b Wall thickness for outside diameters #6.000 inches. c Bearing values are dry pin values per Section d Estimated. 4-18

19 4.2.3 ZK60A Comments and Properties ZK60A is a wrought magnesium-base alloy containing zinc and zirconium. It is available as extruded sections, tubes, and forgings. Increased strength is obtained by artificial aging (T5) from the as-fabricated (F) temper. ZK60A has the best combination of high roomtemperature strength and ductility of the wrought magnesium-base alloys. It is used primarily at temperatures below 300EF. ZK60A has good ductility as compared with other high-strength magnesium alloys and can be formed or bent cold into shapes not possible with those alloys having less ductility. It is not considered a weldable alloy. Material specifications for ZK60A are given in Table (a). Room-temperature mechanical and physical properties are shown in Tables (b) and (c). Elevated temperature curves for physical properties are shown in Figures Table (a). Material Specifications for ZK60A Magnesium Alloy Specification Form ASTM B 107 AMS 4352 AMS 4362 Extrusion Extrusion Die and hand forgings The temper index for ZK60A is as follows: ZK60A-F Temper Section Temper F T ZK60A-T5 Temper Typical room-temperature tension and compression stressstrain curves for extrusions are shown in Figures (a) and (b). Fatigue curves are presented in Figure (a) through (c). 4-19

20 Table (b). Design Mechanical and Physical Properties of ZK60A Magnesium Alloy Extrusion Specification.. ASTM B 107 Form Temper. Cross-sectional area, in. 2. <2.000 Extruded rod, bar, and solid shapes F Extruded hollow shapes All Extruded tube <3.000 in. O.D. Thickness, in... All All All All All wall Basis S S S S S S Mechanical Properties: F tu, ksi: L LT.. F ty, ksi: L LT.. F cy, ksi: L LT.. F su, ksi F a bru, ksi: (e/d = 1.5).. (e/d = 2.0) F a bry, ksi: (e/d = 1.5).. (e/d = 2.0) e, percent: L E, 10 3 ksi. 6.5 E c, 10 3 ksi 6.5 G, 10 3 ksi. 2.4 µ Physical Properties: ω, lb/in C, K, and α.. See Figure a Bearing values are dry pin values per Section

21 Table (c). Design Mechanical and Physical Properties of ZK60A Magnesium Alloy Extrusion and Forging Specification AMS 4352 AMS 4362 Form Temper. Cross-sectional area, in. 2.. < Extruded rod, bar, and solid shapes Extruded hollow shapes T5 Thickness, in... All All All All All All All All Extruded tube <3.000 in. O.D wall in. O.D wall Die forging Hand forging <3.000 <6.000 Basis S S S S S S S S S S S Mechanical Properties: F tu, ksi: L LT.. F ty, ksi: L LT.. F cy, ksi: L LT.. F su, ksi F a bru, ksi: (e/d = 1.5).. (e/d = 2.0) F a bry, ksi: (e/d = 1.5).. (e/d = 2.0) e, percent: L E, 10 3 ksi. 6.5 E c, 10 3 ksi 6.5 G, 10 3 ksi. 2.4 µ Physical Properties: ω, lb/in C, K, and α.. See Figure a Bearing values are dry pin values per Section

22 . - Between 70 F and indicated temperature K - At indicated temperature C - At indicated temperature 16 14, 10-6 in./in./f C, Btu/(lb)(F) C K, Btu/[(hr)(ft 2 )(F)/ft] K Temperature, F Figure Effect of temperature on the physical properties of ZK60A magnesium alloy. 4-22

23 50 40 Stress, ksi Ramberg - Osgood n (RT) = 7.0 TYPICAL Strain, in./in. Figure (a). Typical tensile stress-strain curve for ZK60A-T5 extrusion at room temperature. Figure (b). Typical compressive stress-strain curve for ZK60A-T5 extrusion at room temperature. 4-23

24 .. MMPDS-01 Maximum Stress, ksi x + x + x + x x ZK60A-T5 RT Kt=1.0 Stress Ratio x Runout + + x 20 Note: Stresses are based on net section Fatigue Life, Cycles Figure (a). Best-fit S/N curves for unnotched ZK60A-T5 extruded bar, longitudinal direction. Correlative Information for Figure (a) Product Form: Extruded bar, 0.50 inch diameter Properties: TUS, ksi TYS, ksi Temp.,EF RT (unnotched) Specimen Details: Unnotched inch gross diameter inch net diameter inch root diameter inch long Surface Condition: Polished with No. 240 grit aluminum oxide belt and then a No. 400 grit; polished with kerosene to better than 10 micro-inches Reference: Test Parameters: Loading - Axial Frequency cpm Temperature - RT Environment - Air No. of Heats/Lots: Not specified Equivalent Stress Equation: Log N f = log (S eq -23.7) S eq = S max (1-R) 0.40 Std. Error of Estimate, Log (Life) = 0.60 Standard Deviation, Log (Life) = 0.85 R 2 = 51% Sample Size = 21 [Caution: The equivalent stress model may provide unrealistic life predictions for stress ratios beyond those represented above.] 4-24

25 .. MMPDS-01 Maximum Stress, ksi x + x x + x + + ZK60A-T5 RT Kt=2.4 Stress Ratio x Runout Note: Stresses are based on net section. x x + + x x Fatigue Life, Cycles Figure (b). Best-fit S/N curves for notched, K t = 2.4, ZK60A-T5 extruded bar, longitudinal direction. Correlative Information for Figure (b) Product Form: Extruded bar, 0.50 inch diameter Properties: TUS, ksi TYS, ksi Temp.,EF RT (notched) Specimen Details: Circumferential notched, K t = inch gross diameter inch net diameter inch notch radius 60E flank angle, ω Surface Condition: Ground with aluminum oxide wheel lubricated with sulfur cutting oil; lapped with a copper rod and No. 600 grit alundum lapping compound Reference: Test Parameters: Loading - Axial Frequency cpm Temperature - RT Environment - Air No. of Heats/Lots: Not specified Equivalent Stress Equation: Log N f = log (S eq -13.2) S eq = S max (1-R) 0.42 Std. Error of Estimate, Log (Life) = 0.46 Standard Deviation, Log (Life) = 0.82 R 2 = 69% Sample Size = 30 [Caution: The equivalent stress model may provide unrealistic life predictions for stress ratios beyond those represented above.] 4-25

26 .. MMPDS-01 Maximum Stress, ksi x ZK60A-T5 RT Kt=3.4 Stress Ratio x Runout Note: Stresses are based on net section. x x x x + x + x + + x + + x Fatigue Life, Cycles Figure (c). Best-fit S/N curves for notched, K t = 3.4, ZK60A-T5 extruded bar, longitudinal direction. Correlative Information for Figure (c) Product Form: Extruded bar, 0.50 inch diameter Properties: TUS, ksi TYS, ksi Temp.,EF RT (notched) Frequency cpm Temperature - RT Environment - Air No. of Heats/Lots: Not specified Specimen Details: Circumferential notched, K t = inch gross diameter inch net diameter inch notch radius 60E flank angle, ω Equivalent Stress Equation: Log N f = log (S eq -5.63) S eq = S max (1-R) 0.46 Std. Error of Estimate, Log (Life) = 0.55 Standard Deviation, Log (Life) = 0.99 R 2 = 70% Surface Condition: Ground with aluminum oxide wheel lubricated with sulfur cutting oil; lapped with a copper rod and No. 600 grit alundum lapping compound Sample Size = 36 [Caution: The equivalent stress model may provide unrealistic life predictions for stress ratios beyond those represented above.] Reference: Test Parameters: Loading - Axial 4-26

27 4.3 MAGNESIUM CAST ALLOYS AM100A Comments and Properties AM100A is a magnesium-base casting alloy containing aluminum and a small amount of manganese. It is primarily used as permanent mold castings. AM100A has about the same characteristics as AZ92A. AM100A has less tendency to microshrinkage and hot shortness than the Mg-Al-Zn alloys. It has good weldability and fair pressure tightness. Material specifications for AM100A are given in Table (a). Room-temperature mechanical and physical properties are shown in Table (b). Table (a). Material Specifications for AM100A Magnesium Alloy Specification AMS 4455 AMS 4483 a a Noncurrent specification. Form Investment casting Permanent mold casting 4-27

28 Table (b). Design Mechanical and Physical Properties of AM100A Magnesium Alloy Casting Specification. AMS 4455 AMS 4483 a Form.. Investment casting Permanent mold casting Temper T6 T6 Location within casting.. Any area Basis.. S S Mechanical Properties c : F tu, ksi F ty, ksi F cy, ksi.. F su, ksi.. F bru, ksi: (e/d = 1.5). (e/d = 2.0). F bry, ksi: (e/d = 1.5). (e/d = 2.0). e, percent E, 10 3 ksi E c, 10 3 ksi G, 10 3 ksi µ. Physical Properties: ω, lb./in. 3 C, K, and α.. 17 c 9.5 c b a Noncurrent specification. b Reference should be made to the specific requirements of the procuring or certificating agency with regard to the use of the above values in the design of castings. c When specified on drawing, conformance to tensile property requirements is determined by testing specimens cut from castings. 17 c 10 c

29 4.3.2 AZ91C/AZ91E Comments and Properties AZ91C is a magnesium-base casting alloy containing aluminum and zinc. AZ91E is a version which contains a significantly lower level of impurities resulting in improved corrosion resistance. These alloys have good castability with a good combination of ductility and strength. AZ91C and AZ91E are the most commonly used sand castings for temperatures under 300EF. AZ91C is available as sand and investment castings, while AZ91E is available as a sand casting. AZ91C and AZ91E have fair weldability and pressure tightness. Some material specifications covering AZ91C/AZ91E are presented in Table (a). Roomtemperature mechanical and physical properties are shown in Tables (b) and (c). Table (a). Material Specifications for AZ91C/AZ91E Magnesium Alloy Specification Form AMS 4437 AMS 4452 AMS 4446 Sand casting Investment casting Sand casting The temper index for AZ91C/AZ91E is as follows: Section Temper T T6 Temper Figure contains an elevated temperature curve for tension and compression moduli. Typical tensile stress-strain curves at room temperature and several elevated temperatures are presented in Figure

30 Table (b). Design Mechanical and Physical Properties of AZ91C Magnesium Alloy Casting Specification. AMS 4437 AMS 4452 Form. Sand casting Investment casting Temper.. T6 T6 Location within casting. Any area Basis.. S S Mechanical Properties a : F tu, ksi F ty, ksi.. F cy, ksi.. F su, ksi.. F bru, ksi: (e/d = 1.5). (e/d = 2.0). F bry, ksi: (e/d = 1.5). (e/d = 2.0). e, percent.. E, 10 3 ksi E c, 10 3 ksi.. G, 10 3 ksi µ. Physical Properties: ω, lb./in. 3.. C,Btu/(lb)(EF).. K, Btu/[(hr)(ft 2 )(EF)/ft].. α, 10-6 in./in./ef. 17 b 12 b b c 41 (212EF to 572EF) 14 (65EF to 212EF) a Reference should be made to the specific requirements of the procuring or certificating agency with regard to the use of the above values in the design of castings. b When specified on drawing, conformance to tensile property requirements is determined by testing specimens cut from castings. c Estimated. 17 b 12 b 12 1 b 4-30

31 Table (c). Design Mechanical and Physical Properties of AZ91E Magnesium Alloy Casting Specification.. AMS 4446 Form Sand casting Condition.. T6 Location within casting Any area Basis S Mechanical Properties a : F tu, ksi F ty, ksi F cy, ksi 12 F su, ksi F bru, ksi: (e/d = 1.5).. (e/d = 2.0).. F bry, ksi: (e/d = 1.5).. (e/d = 2.0).. e, percent. E, 10 3 ksi. 6.5 E c, 10 3 ksi 6.5 G, 10 3 ksi. 2.4 µ Physical Properties: ω, lb/in C, Btu/(lb)(EF) c K, Btu/[(hr)(ft 2 )(EF)/ft].. 41 (212EF to 572EF) α, 10-6 in./in./f 14 (65EF to 212EF) 17 b 12 b a b c Reference should be made to the specific requirements of the procuring or certificating agency with regard to the use of the above values in the design of castings. When specified on drawing, conformance to tensile property requirements is determined by testing specimens cut from castings. Estimated. 4-31

32 . MMPDS Percentage of Room Temperature Modulus Modulus at temperature Exposure up to 1/2 hr TYPICAL E & E c Temperature, F Figure Effect of temperature on the tensile and compressive moduli (E and E c ) of cast AZ91C-T6/AZ91E-T /2 -hr exposure RT F 400 F Stress, ksi Ramberg - Osgood n (RT) = 4.5 n (300 F) = 3.9 n (400 F) = 5.3 TYPICAL Strain, in./in. Figure Typical tensile stress-strain curves for cast AZ91C-T6/AZ91E-T6 at room and elevated temperatures. 4-32

33 4.3.3 AZ92A Comments and Properties AZ92A is a magnesium-base casting alloy containing aluminum and zinc. It is slightly stronger and less ductile than AZ91C but is much like it in other characteristics. It is available as sand and permanent-mold casting. AZ92A has fair weldability and pressure tightness. Material specifications for AZ92A are presented in Table (a). Room-temperature mechanical and physical properties are shown in Table (b). Elevated temperature curves for physical properties are shown in Figure Table (a). Material Specifications for AZ92A Magnesium Alloy Specification AMS 4434 AMS 4484 a AMS 4453 a Noncurrent specification. Form Sand casting Permanent-mold casting Investment casting The temper index for AZ92A is as follows: Section Temper T AZ92A-T6 Temper Elevated temperature curves for various mechanical properties are presented in Figures (a) through (c), and Typical stress-strain and tangent-modulus curves at room temperature and several elevated temperatures are shown in Figures (a) and (b). 4-33

34 Table (b). Design Mechanical and Physical Properties of AZ92A Magnesium Alloy Casting Specification AMS 4484 a AMS 4434 AMS 4453 Form. Permanent mold casting Sand casting Investment Casting Temper.. T6 T6 T6 Location within casting. Any area Basis. S S S Mechanical Properties b : F tu, ksi.. F ty, ksi.. F cy, ksi. F su, ksi. F bru, ksi: (e/d = 1.5) (e/d = 2.0) F bry, ksi: (e/d = 1.5) (e/d = 2.0) e, percent.. E, 10 3 ksi.. E c, 10 3 ksi.. G, 10 3 ksi.. µ Physical Properties: ω, lb./in. 3.. C, Btu/(lb)(EF). K and α. 17 c 13.5 c c 13.5 c d See Figure a b c d Noncurrent specification. Reference should be made to the specific requirements of the procuring or certificating agency with regard to the use of the above values in the design of castings. When specified on drawing, conformance to tensile property requirements is determined by testing specimens cut from castings. Estimated. 4-34

35 . - Between 70 F and indicated temperature K - At indicated temperature K, Btu/[(hr)(ft 2 )(F)/ft] K , 10-6 in./in./f Temperature, F Figure Effects of temperature on the physical properties of cast AZ92A-T

36 100 Strength at temperature Exposure up to 1000 hr 80 Percent F tu at Room Temperature hr 1/2 hr Temperature, F Figure (a). Effect of temperature on the tensile ultimate strength (F tu ) of cast AZ92A-T Strength at temperature Exposure up to 1000 hr 80 Percent F ty at Room Temperature hr 1/2 hr Temperature, F Figure (b). Effect of temperature on the tensile yield strength (F ty ) of cast AZ92A-T

37 .. MMPDS F tu F ty Percentage of Room Temperature Strength Strength at room temperature Exposure up to 1000 hr Temperature, F Figure (c). Effect of exposure at elevated temperature on the roomtemperature tensile ultimate strength (F tu ) and the tensile yield strength (F ty ) of cast AZ92A-T Percentage of Room Temperature Modulus Modulus at temperature Exposure up to 1/2 hr TYPICAL E & E c Temperature, F Figure Effect of temperature on the tensile and compressive moduli (E and E c ) of cast AZ92A-T

38 25 20 Compression Compression Stress, ksi TYPICAL Strain, in./in. Compressive Tangent Modulus, 10 3 ksi Figure (a). Typical compressive stress-strain and compressive tangentmodulus curves for cast AZ92A-T6 at room temperature. 25 RT F Stress, ksi F 5 1/2-hr exposure 0 TYPICAL Strain, in./in. Figure (b). Typical tensile stress-strain curves for cast AZ92A-T6 at room and elevated temperatures. 4-38

39 4.3.4 EZ33A Comments and Properties EZ33A is a magnesium-base casting alloy containing rare earths, zinc, and zirconium. It is available as sand castings in the artificially aged (T5) temper. EZ33A has lower strength than the Mg-Al-Zn alloys at room temperature but is less affected by increasing temperature. It is generally used for applications at temperatures of 300 to 500EF. EZ33A castings are very sound and are sometimes used for pressure tightness. It has good stability in the T5 temper and excellent weldability. It is sometimes used for applications requiring good damping ability. A material specification for EZ33A is presented in Table (a). Room-temperature mechanical and physical properties are shown in Table (b). The effect of temperature on physical properties is shown in Figure Table (a). Material Specification for EZ33A Magnesium Alloy Specification AMS 4442 Sand casting Form The temper index for EZ33A is as follows: Section Temper T EZ33A-T5 Temper Elevated temperature curves for tensile properties are presented in Figures (a) through (c). A typical tensile stress-strain curve at room temperature is presented in Figure

40 Table (b). Design Mechanical and Physical Properties of EZ33A Magnesium Alloy Casting Specification AMS 4442 Form. Temper.. Location within casting.. Basis. Mechanical Properties a : F tu, ksi.. F ty, ksi.. F cy, ksi.. F su, ksi.. F bru, ksi: (e/d = 1.5). (e/d = 2.0). F bry, ksi: (e/d = 1.5). (e/d = 2.0). e, percent.. E, 10 3 ksi E c, 10 3 ksi.. G, 10 3 ksi.. µ Physical Properties: ω, lb/in. 3 C, Btu/(lb)(EF). K and α. Sand casting T5 Any area S 13 b 11 b See Figure a b Reference should be made to the specific requirements of the procuring or certificating agency with regard to the use of the above values in the design of castings. When specified on drawing, conformance to tensile property requirements is determined by testing specimens cut from castings. 4-40

41 . - Between 70 F and indicated temperature K - At indicated temperature K, Btu/[(hr)(ft 2 )(F)/ft] K, T , 10-6 in./in./f Temperature, F Figure Effect of temperature on the physical properties of cast EZ33A. 4-41

42 Figure (a). Effect of temperature on the tensile ultimate strength (F tu ) of cast EZ33A-T5. Figure (b). Effect of temperature on the tensile yield strength (F ty ) of cast EZ33A-T

43 Figure (c). Effect of exposure at elevated temperatures on the room temperature tensile ultimate strength (F tu ) and the tensile yield strength (F ty ) of cast EZ33A-T Stress, ksi 10 Ramberg - Osgood n (RT) = 15 5 TYPICAL Strain, in./in. Figure Typical tensile stress-strain curve for cast EZ33A-T5 at room temperature. 4-43

44 4.3.5 QE22A Comments and Properties QE22A is a magnesium-base alloy containing silver, rare earths in the form of didymium, and zirconium. It is available as sand and permanent-mold castings. It is used in the solution heat-treated and artificially aged (T6) condition where a high yield strength is needed at temperatures up to 600EF. QE22A has good weldability and fair pressure tightness. Material specifications for QE22A are presented in Table (a). Room-temperature mechanical and physical properties are shown in Table (b). Table (a). Material Specifications for QE22A Magnesium Alloy Specification AMS 4418 Sand casting Form The temper index for QE22A is as follows: Section Temper T QE22A-T6 Temper Elevated temperature curves for various tensile properties and modulus of elasticity are presented in Figures and Typical tensile stress-strain curves at various temperatures from room temperature through 700EF are shown in Figure

45 Table (b). Design Mechanical and Physical Properties of QE22A Magnesium Alloy Casting Specification. AMS 4418 Form.. Temper.. Location within casting.. Basis.. Mechanical Properties a : F tu, ksi F ty, ksi F cy, ksi F su, ksi F bru, ksi: (e/d = 1.5).. (e/d = 2.0).. F bry, ksi: (e/d = 1.5).. (e/d = 2.0).. e, percent. E, 10 3 ksi. E c, 10 3 ksi G, 10 3 ksi µ. Physical Properties: ω, lb/in. 3. C, Btu/(lb)(EF).. K, Btu/[(hr)(ft 2 )(EF)/ft].. α, 10-6 in./in./ef. Sand casting T6 Any area S 32 b 23 b 23 2 b c (68EF to 392EF) a Reference should be made to the specific requirements of the procuring or certificating agency with regard to the use of the above values in the design of castings. b When specified on drawing, conformance to tensile property requirements is determined by testing specimens cut from castings. c Estimated. 4-45

46 Figure Effect of temperature on the tensile ultimate strength (F tu ) and the tensile yield strength (F ty ) of cast QE22A-T6. Figure Effect of temperature on the tensile modulus (E) of cast QE22A-T

47 50.5 -hr exposure Stress, ksi Ramberg - Osgood n (RT) = 6.5 n (300 F) = 7.9 n (400 F) = 9.0 n (500 F) = 6.3 n (600 F) = 4.8 n (700 F) = 3.9 TYPICAL 400 F 500 F 300 F RT F F Strain, in./in. Figure Typical tensile stress-strain curves for cast QE22A-T6 at room and elevated temperatures. 4-47

48 4.3.6 ZE41A Comments and Properties ZE41A is a magnesium-base casting alloy containing zinc, zirconium, and rare earth elements. It is available as sand or permanent-mold castings in the artificially aged temper (T5). ZE41A has a higher yield strength than the Mg-Al-Zn alloys at room temperature and is more stable at elevated temperatures. It is useful for applications at temperatures up to 320EF. ZE41A castings possess good weldability and are pressure tight. A material specification for ZE41A is presented in Table (a). Room temperature mechanical and physical properties are shown in Table (b). The effect of temperature on thermal conductivity is shown in Figure Table (a). Material Specification for ZE41A Magnesium Alloy Specification AMS 4439 Form Sand casting The temper index for ZE41A is as follows: Section Temper T T5 Temper Elevated temperature curves for tensile yield and ultimate strengths are presented in Figure The effect of temperature on the tensile modulus of elasticity is shown in Figure Figures (a) and (b) contain tensile and compressive stress-strain curves as well as a compressive tangent-modulus curve. 4-48

49 Table (b). Design Mechanical and Physical Properties of ZE41A Magnesium Alloy Casting Specification.. AMS 4439 Form Sand casting Temper. T5 Thickness, in... Any area Basis S Mechanical Properties a : F tu, ksi 26 b F ty, ksi 17.5 b F cy, ksi 15 F su, ksi 17 F c bru, ksi: (e/d = 1.5).. 38 (e/d = 2.0).. 49 F c bry, ksi: (e/d = 1.5).. 31 (e/d = 2.0).. 35 e, percent. 2 b E, 10 3 ksi. 6.5 E c, 10 3 ksi 6.5 G, 10 3 ksi. 2.4 µ Physical Properties: ω, lb/in C, Btu/(lb)(EF) (at 68EF) K, Btu/[(hr)(ft 2 )(EF)/ft].. See Figure α, 10-6 in./in./ef (68 to 212EF) a The mechanical properties shown are reliably obtainable when castings are produced under the quality assurance provisions of AMS These provisions require preproduction approval, documentation of foundry procedures, and specific testing procedures for the acceptance of each production lot of castings. Strict adherence to these requirements is mandatory if these properties are to be reliably assured in each casting. b Conformance to tensile property requirements is determined by testing specimens cut from casting only when specified on drawing. c Bearing values are dry pin values per Section

50 Figure Effect of temperature on the thermal conductivity (K) of ZE41A-T5 sand casting. 4-50

51 Figure Effect of temperature on the tensile ultimate strength (F tu ) and tensile yield strength (F ty ) of ZE41A-T5 sand casting. Figure Effect of temperature on the tensile modulus (E) of ZE41A-T5 sand casting. 4-51

52 Figure (a). Typical tensile stress-strain curves for ZE41A-T5 sand casting at room and elevated temperatures Stress, ksi 10 5 Ramberg - Osgood n (compression) = 3.7 TYPICAL Strain, in./in. Compressive Tangent Modulus, 10 3 ksi Figure (b). Typical compressive stress-strain and tangent-modulus curves for ZE41A-T5 sand casting at room temperature. 4-52

53 4.4 ELEMENT PROPERTIES BEAMS Refer to Chapter 1 and References 1.7.1(a) and (b) for general information on stress analysis of beams Simple Beams Beams of solid tubular, or similar cross sections can be assumed to fail through exceeding an allowable modulus of rupture in bending (F b ). In the absence of specific data, the ratio F b /F tu can be assumed to be 1.25 for solid sections Round Tubes For round tubes, the value of F b will depend on the D/t ratio as well as the compressive yield stress Unconventional Cross Sections Sections other than solid or tubular should be tested to determine allowable bending stress Built-Up Beams Built-up beams will usually fail because of local failure of component parts Thin-Web Beams The allowable stress for thin-web beams will depend on the nature of the failure and are determined from the allowable stress of the web in tension and of the flanges or stiffeners in compression COLUMNS Primary Failure The general formula for primary instability is given in Section Formulas applicable to magnesium-alloy columns are given in Tables (a) and (b). See References 4.4.2(a) and (b). Table (a). Column Formula for Magnesium-Alloy Extruded Open Shapes General Formula a P A ' K(F cy )n (LN/ρ) m (Stress values are in ksi) Alloy K n m Max. P/A AZ31B, AZ61A ZK60A-T5 2,900 3,300 ¼ ¼ F cy 0.96 F cy aformula is for members that do not fail by local buckling. See Figure (a). 4-53