Magnesium Alloy AZ91E-T4
Temper
ASTM AZ91E · UNS M11919
T4 = solution heat treated and naturally aged
Pick when maximum ductility, toughness and impact resistance matter more than yield strength.
Values for the T4 condition
Other AZ91E tempers and conditions
AZ91E is listed in 4 conditions; see the grade overview at AZ91E.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
T4This page Solution heat treated and naturally aged | Pick when maximum ductility, toughness and impact resistance matter more than yield strength. | 90 | 275 | 14 | 55 HB | 72 W/m·K |
As fabricated | Lowest-cost as-cast condition for non-critical housings and covers where ductility and strength are not driving. | 97 | 165 | 2.5 | 60 HB | 51 W/m·K |
Cooled from hot working and artificially aged | Low-distortion, low-cost aging of as-cast parts giving a modest hardness/yield gain without a solution soak. | 110 | 165 | 2 | 66 HB | 10 % IACS |
T6Default Solution heat treated and artificially aged | Standard structural condition: best combination of yield strength, hardness and fatigue for gearbox and housing castings. | 145 | 275 | 6 | 70 HB | 72 W/m·K |
What is AZ91E-T4?
AZ91E-T4 is AZ91E in the T4 temper — pick when maximum ductility, toughness and impact resistance matter more than yield strength. AZ91E-T4 has a yield strength of 90 MPa (13.1 ksi) and a tensile strength of 275 MPa (39.9 ksi) — weaker than 96% of magnesium alloy grades. Elongation at break is 14% and the elastic modulus is 45 GPa (6.53 Msi). AZ91E-T4 has a density of 1.81 g/cm³ (0.0654 lb/in³), heavier than 58% of magnesium alloy grades. It melts at 470°C (878 °F). T6 is the default condition FabDigit quotes; T4 is available on request or by drawing note.
Advantages
- Good corrosion resistance — 32/100, better than 96% of magnesium alloy grades
- Ductile — tolerates forming and impact — 14%, better than 83% of magnesium alloy grades
Limitations
- Low strength — 90 MPa (13.1 ksi), worse than 96% of magnesium alloy grades
- Limited service temperature — 120°C (248 °F), worse than 78% of magnesium alloy grades
- Low electrical conductivity — 12 % IACS, worse than 78% of magnesium alloy grades
AZ91E-T4 properties
Typical room-temperature values for AZ91E-T4; 13 are specific to this condition. Other listed values are AZ91E reference data and may not represent this condition. Bars are the position among magnesium alloy grades.
Physical3
AZ91E-T4 has a density of 1.81 g/cm³ (0.0654 lb/in³), heavier than 58% of magnesium alloy grades. It melts at 470°C (878 °F).
Mechanical14
AZ91E-T4 has a yield strength of 90 MPa (13.1 ksi) and a tensile strength of 275 MPa (39.9 ksi) — weaker than 96% of magnesium alloy grades. Elongation at break is 14% and the elastic modulus is 45 GPa (6.53 Msi).
Thermal6
AZ91E-T4 is rated for continuous service to 120°C (248 °F). It conducts heat at 72 W/m·K (41.6 BTU/hr·ft·°F), worse than 69% of magnesium alloy grades. Thermal expansion is 26 µm/m·K (14.4 µin/in·°F).
Electrical3
AZ91E-T4 conducts electricity at 12 % IACS, worse than 78% of magnesium alloy grades.
Chemical & Environmental3
Corrosion resistance is poor (32/100), better than 96% of magnesium alloy grades.
Sustainability4
Producing a kilogram of AZ91E-T4 takes about 330 MJ of energy and emits 30 kg of CO₂ — less than 56% of magnesium alloy grades. Typical recycled content is 15%.
Manufacturability8
AZ91E-T4's machinability is excellent (93/100, worse than 78% of magnesium alloy grades); weldability very good (70/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with AZ91E-T4
Is AZ91E easy to machine?
Cuts extremely freely at high speed with sharp positive-rake tools and low forces; use dry or mineral-oil cutting (never water-based) and manage fine chips/dust for fire risk.
Can AZ91E be welded?
Readily GTAW/GMAW welded with AZ92A or AZ101A filler under Ar; preheat thick sections and re-solution/age or stress-relieve to restore properties and avoid SCC.
Can AZ91E be formed, bent or molded?
Sand and permanent-mold casting alloy with excellent fluidity; needs SF6-free protective cover gas or flux, generous feeding and hot-tearing-aware gating — no cold forming.
What surface finishes work on AZ91E?
Requires chromate-free conversion coating (or Dow 17 / HAE / PEO) plus epoxy primer and topcoat; isolate all steel/aluminium fasteners to prevent galvanic attack.
AZ91E 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 | 8.1 – 9.3 | 8.7 |
| Zn | 0.4 – 1 | 0.7 |
| Mnmin Mn also tied to Fe/Mn ratio control | 0.17 – 0.35 | 0.25 |
| Si | ≤ 0.2 | — |
| Cuhigh-purity limit vs 0.10 for AZ91C | ≤ 0.02 | — |
| Nihigh-purity limit | ≤ 0 | — |
| Fehigh-purity limit — key to corrosion performance | ≤ 0.01 | — |
| Other (each) | ≤ 0.01 | — |
| Others (total) | ≤ 0.3 | — |
| Mg | balance | — |
AZ91E-T4 — frequently asked
What is AZ91E-T4 used for?
AZ91E-T4 is typically used for structural sand castings, aerospace and helicopter gearbox housings, corrosion-exposed equipment enclosures, permanent-mold pump and valve bodies, motorsport suspension and chassis castings and portable equipment frames. In short: high-purity AZ91 casting grade; best ductility in family; weldable structural magnesium.
What is the yield strength of AZ91E-T4?
AZ91E-T4 has a typical yield strength of 90 MPa (13.1 ksi) and a tensile strength of 275 MPa (39.9 ksi) — weaker than 96% of magnesium alloy grades. Strength varies by condition: see the 4 listed tempers.
Is AZ91E-T4 easy to machine?
Yes — machinability is rated excellent (93/100, worse than 78% of magnesium alloy grades). Cuts extremely freely at high speed with sharp positive-rake tools and low forces; use dry or mineral-oil cutting (never water-based) and manage fine chips/dust for fire risk.
Can AZ91E-T4 be welded?
Yes — weldability is rated very good (70/100). Readily GTAW/GMAW welded with AZ92A or AZ101A filler under Ar; preheat thick sections and re-solution/age or stress-relieve to restore properties and avoid SCC.
What surface finishes work on AZ91E-T4?
Requires chromate-free conversion coating (or Dow 17 / HAE / PEO) plus epoxy primer and topcoat; isolate all steel/aluminium fasteners to prevent galvanic attack.
Can AZ91E-T4 be formed, bent or molded?
Sand and permanent-mold casting alloy with excellent fluidity; needs SF6-free protective cover gas or flux, generous feeding and hot-tearing-aware gating — no cold forming.
What is the maximum service temperature of AZ91E-T4?
AZ91E-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 AZ91E-T6 and AZ91E-T4?
T6 is the default condition — standard structural condition: best combination of yield strength, hardness and fatigue for gearbox and housing castings. T4: pick when maximum ductility, toughness and impact resistance matter more than yield strength. Yield strength is 145 MPa in T6 versus 90 MPa in T4.
Sources
- ASTM B80 — Magnesium-Alloy Sand Castings — ASTM International (2015)
- ASTM B199 — Magnesium-Alloy Permanent Mold Castings — ASTM International (2019)
- ASTM B93/B93M — Magnesium Alloys in Ingot Form for Sand, Permanent Mold and Die Castings — ASTM International (2020)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Specialty Handbook: Magnesium and Magnesium Alloys — ASM International (1999)
- SAE AMS 4446 / UNS M11919 designation data — SAE International (2018)
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.