Magnesium Alloy AZ81A-T4
Temper · default condition
ASTM AZ81A · UNS M11810
T4 = solution heat treated and naturally aged
The standard supply condition for AZ81A — best combination of tensile strength, elongation and impact toughness for pressure-tight aerospace sand castings.
Values for the T4 condition
Other AZ81A tempers and conditions
AZ81A is listed in 2 conditions; see the grade overview at AZ81A.
- T4
- F
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
T4DefaultThis page Solution heat treated and naturally aged | The standard supply condition for AZ81A — best combination of tensile strength, elongation and impact toughness for pressure-tight aerospace sand castings. | 83 | 275 | 15 | 55 HB | 11.3 % IACS |
As fabricated | Pick only for non-critical castings or when the part is to be heat treated later; ductility is low because of the coarse Mg17Al12 network. | 85 | 160 | 3 | 60 HB | 12.2 % IACS |
What is AZ81A-T4?
AZ81A-T4 is AZ81A in the T4 temper — the standard supply condition for AZ81A — best combination of tensile strength, elongation and impact toughness for pressure-tight aerospace sand castings. AZ81A-T4 has a yield strength of 83 MPa (12 ksi) and a tensile strength of 275 MPa (39.9 ksi) — weaker than 99% of magnesium alloy grades. Elongation at break is 15% and the elastic modulus is 45 GPa (6.53 Msi). AZ81A-T4 has a density of 1.8 g/cm³ (0.065 lb/in³), lighter than 63% of magnesium alloy grades. It melts at 490°C (914 °F).
Advantages
- Ductile — tolerates forming and impact — 15%, better than 87% of magnesium alloy grades
Limitations
- Low strength — 83 MPa (12 ksi), worse than 99% of magnesium alloy grades
- Poor heat conductor — 51 W/m·K (29.5 BTU/hr·ft·°F), worse than 97% of magnesium alloy grades
- Low electrical conductivity — 11.3 % IACS, worse than 96% of magnesium alloy grades
- Hard to polish — 45/100, worse than 93% of magnesium alloy grades
- Limited service temperature — 120°C (248 °F), worse than 78% of magnesium alloy grades
AZ81A-T4 properties
Typical room-temperature values for AZ81A-T4; 17 are specific to this condition. Other listed values are AZ81A reference data and may not represent this condition. Bars are the position among magnesium alloy grades.
Physical3
AZ81A-T4 has a density of 1.8 g/cm³ (0.065 lb/in³), lighter than 63% of magnesium alloy grades. It melts at 490°C (914 °F).
Mechanical13
AZ81A-T4 has a yield strength of 83 MPa (12 ksi) and a tensile strength of 275 MPa (39.9 ksi) — weaker than 99% of magnesium alloy grades. Elongation at break is 15% and the elastic modulus is 45 GPa (6.53 Msi).
Thermal6
AZ81A-T4 is rated for continuous service to 120°C (248 °F). It conducts heat at 51 W/m·K (29.5 BTU/hr·ft·°F), worse than 97% of magnesium alloy grades. Thermal expansion is 26 µm/m·K (14.4 µin/in·°F).
Electrical3
AZ81A-T4 conducts electricity at 11.3 % IACS, worse than 96% of magnesium alloy grades.
Chemical & Environmental3
Corrosion resistance is poor (18/100), worse than 88% of magnesium alloy grades.
Sustainability4
Producing a kilogram of AZ81A-T4 takes about 350 MJ of energy and emits 30 kg of CO₂ — more than 74% of magnesium alloy grades. Typical recycled content is 30%.
Manufacturability8
AZ81A-T4's machinability is excellent (95/100, better than 54% of magnesium alloy grades); weldability good (62/100); formability poor (15/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with AZ81A-T4
Is AZ81A easy to machine?
Outstanding machinability — very high speeds, low cutting forces, sharp positive-rake tools, no coolant containing water where possible, and strict chip/fines fire control (never water-quench a Mg fire).
Can AZ81A be welded?
GTAW/GMAW weldable with AZ92A or AZ101A filler; preheat 250–300 °C for heavy sections, then re-solution treat (T4) to restore ductility and relieve stress in the HAZ.
Can AZ81A be formed, bent or molded?
Sand and permanent-mold casting alloy with good fluidity and pressure tightness; needs melt protection (SF6-free cover gas), grain refinement by superheat, and generous fillets to avoid hot tearing — no cold forming.
What surface finishes work on AZ81A?
Always apply a chromate-free conversion coat or Mg anodic/PEO coating (Dow 17, HAE) plus epoxy primer/topcoat; isolate from steel and aluminium fasteners to prevent galvanic attack.
AZ81A chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Al | 7 – 8.1 | 7.6 |
| Zn | 0.4 – 1 | 0.7 |
| Mn0.13 % min required for corrosion control | 0.13 – 0.35 | 0.2 |
| Si | ≤ 0.3 | — |
| Cu | ≤ 0.1 | — |
| Ni | ≤ 0.01 | — |
| Fehigh-purity limit | ≤ 0.01 | — |
| Others (each)0.30 % max total | ≤ 0.1 | — |
| Mg | balance | — |
AZ81A-T4 — frequently asked
What is AZ81A-T4 used for?
AZ81A-T4 is typically used for pressure-tight housings, aerospace sand castings, gearbox and accessory-drive cases, hydraulic and pneumatic valve bodies, instrument and avionics enclosures and permanent-mould covers and manifolds. In short: most ductile Mg casting; pressure-tight aerospace castings; solution-treated T4 supply.
What is the yield strength of AZ81A-T4?
AZ81A-T4 has a typical yield strength of 83 MPa (12 ksi) and a tensile strength of 275 MPa (39.9 ksi) — weaker than 99% of magnesium alloy grades. Strength varies by condition: see the 2 listed tempers.
Is AZ81A-T4 easy to machine?
Yes — machinability is rated excellent (95/100, better than 54% of magnesium alloy grades). Outstanding machinability — very high speeds, low cutting forces, sharp positive-rake tools, no coolant containing water where possible, and strict chip/fines fire control (never water-quench a Mg fire).
Can AZ81A-T4 be welded?
Yes — weldability is rated good (62/100). GTAW/GMAW weldable with AZ92A or AZ101A filler; preheat 250–300 °C for heavy sections, then re-solution treat (T4) to restore ductility and relieve stress in the HAZ.
What surface finishes work on AZ81A-T4?
Always apply a chromate-free conversion coat or Mg anodic/PEO coating (Dow 17, HAE) plus epoxy primer/topcoat; isolate from steel and aluminium fasteners to prevent galvanic attack.
Can AZ81A-T4 be formed, bent or molded?
Sand and permanent-mold casting alloy with good fluidity and pressure tightness; needs melt protection (SF6-free cover gas), grain refinement by superheat, and generous fillets to avoid hot tearing — no cold forming.
What is the maximum service temperature of AZ81A-T4?
AZ81A-T4 is rated for continuous use to about 120°C (248 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between AZ81A-T4 and AZ81A-F?
T4 is the default condition — the standard supply condition for AZ81A — best combination of tensile strength, elongation and impact toughness for pressure-tight aerospace sand castings. F: pick only for non-critical castings or when the part is to be heat treated later; ductility is low because of the coarse Mg17Al12 network. Yield strength is 83 MPa in T4 versus 85 MPa in F.
Sources
- ASTM B80 — Magnesium-Alloy Sand Castings — ASTM International (2015)
- SAE AMS 4453 / UNS M11810 designation records — SAE International (2018)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Specialty Handbook: Magnesium and Magnesium Alloys — ASM International (1999)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.