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SAE J466 Magnesium Wrought Alloys: Composition, Properties, and Engineering Best Practices
SAE J466 (2018) is the definitive standard for magnesium wrought alloys, specifying chemical composition limits and minimum mechanical properties for common alloys in sheet, plate, extrusion, forging, and tube forms. Whether you’re designing lightweight structures for automotive, aerospace, or industrial equipment, understanding these specifications ensures material performance and procurement accuracy. This article breaks down the key alloy families, temper options, and practical design considerations.
Chemical Composition and Temper Designations
All magnesium wrought alloys covered by SAE J466 are listed with precise weight percent ranges for alloying elements. The standard also cross-references equivalent ASTM, AMS, and military specifications. Temper designations follow ASTM B296, with -0 for annealed (maximum formability), -H24 for strain-hardened and partially annealed (higher strength), and -T tempers for heat-treated conditions.
| Alloy (UNS/SAE) | Al | Mn (min) | Zn | Zr | RE (Mischmetal) | Th | Li | Others (each max) |
|---|---|---|---|---|---|---|---|---|
| AZ31B (M11311) | 2.5–3.5 | 0.20 | 0.6–1.4 | — | — | — | — | 0.30 |
| AZ61A (M11610) | 5.8–7.2 | 0.15 | 0.40–1.5 | — | — | — | — | 0.30 |
| AZ80A (M11800) | 7.8–9.2 | 0.12 | 0.20–0.8 | — | — | — | — | 0.30 |
| HK31A (M13310) | — | — | 0.30 max | 0.40–1.0 | — | 2.5–4.0 | — | 0.30 |
| HM21A (M13210) | — | 0.45–1.1 | — | — | — | 1.5–2.5 | — | 0.30 |
| HM31A (M13312) | — | 1.2 | — | — | — | 2.5–3.5 | — | 0.30 |
| LA141A (M14141) | 1.0–1.5 | 0.15 | — | — | — | — | 13–15 | 0.30 |
| M1A (M15100) | — | 1.2 | — | — | — | — | — | 0.30 |
| ZE10A (M16100) | — | — | 1.0–1.5 | — | 0.12–0.22 | — | — | 0.30 |
| ZK40A (M16400) | — | — | 3.5–4.5 | 0.45 min | — | — | — | 0.30 |
| ZK60A (M16600) | — | — | 4.8–6.2 | 0.45 min | — | — | — | 0.30 |
🛠️ Design Insight: The -0 temper is ideal for complex forming operations, while -H24 balances strength and ductility for structural panels and tooling plate. Always verify temper availability with your supplier.
Mechanical Properties and Forms Available
Mechanical property tables in SAE J466 list minimum tensile strength, yield strength (0.2% offset), and elongation for each alloy and temper. Properties vary significantly with thickness and temper. For example, AZ31B sheet in -H24 temper achieves 39,000 psi (269 MPa) tensile strength at thicknesses 0.016–0.249 in, with 6% elongation. Plate thicknesses above 2.0 in have reduced strength but still meet minimum requirements.
| Temper | Thickness (in) | Tensile Strength (psi) | Yield Strength (psi) | Elongation (%) |
|---|---|---|---|---|
| -0 | 0.016–0.250 | 32,000 (221 MPa) max 40,000 | — | 12 |
| -H24 | 0.016–0.249 | 39,000 (269 MPa) | 29,000 (200 MPa) | 6 |
| -H24 | 0.251–0.374 | 38,000 (262 MPa) | 26,000 (179 MPa) | 8 |
| -H24 | 0.375–0.500 | 37,000 (255 MPa) | 24,000 (165 MPa) | 8 |
Other forms such as extrusions, forgings, and tube have their own property tables. Alloy AZ31B is the most commonly used sheet alloy, while ZK60A offers higher strength for extruded shapes. HK31A and HM21A are preferred for elevated-temperature service up to 700°F (371°C).
Engineering Considerations and Common Pitfalls
Working with magnesium alloys requires attention to temperature and temper. Forming: Most operations should be performed hot (300–750°F) to avoid cracking. Annealed alloys offer maximum workability. Joining: Adhesive bonding, spot welding, riveting, and bolting are all suitable. Fusion welding is possible; some alloys (e.g., AZ31B) require stress relief after welding, while ZE10A does not. Machining: Magnesium alloys machine readily, but fine chips are flammable—always follow safe machining practices.
⚠️ Common Mistake: Assuming magnesium tempers are identical to aluminum. Always use ASTM B296 for magnesium temper definitions. Also, never cold-form complex shapes without preheating—cracking is likely.
Frequently Asked Questions
What are the minimum tensile and yield strengths for AZ31B in -H24 temper?
For 0.016–0.249 in thickness, minimum tensile strength is 39,000 psi (269 MPa) and yield strength is 29,000 psi (200 MPa) with 6% elongation.
Which magnesium alloy is best for elevated temperature applications?
HK31A (M13310) and HM21A (M13210) were developed for use up to 700°F (371°C) and are commonly used in aircraft and missiles.
What are the key differences between sheet and plate in SAE J466?
Sheet is defined as thickness 0.006–0.249 in (0.15–6.32 mm), while plate is 0.250 in (6.35 mm) or thicker. Dimensional tolerances follow ASTM B90 and are similar to aluminum alloys.
For detailed procurement and design, always reference the latest SAE J466 specification and consult the cross-referenced ASTM or AMS standards. Understanding these basics will help you avoid common pitfalls and leverage the lightweight advantage of magnesium alloys.
