Magnesium Alloy AZ91C-T6
Temper
ASTM AZ91C · UNS M11914
T6 = solution heat treated and artificially aged
Highest-strength condition for structural sand/permanent-mold castings where yield strength and hardness matter more than ductility.
Values for the T6 condition
Other AZ91C tempers and conditions
AZ91C is listed in 4 conditions; see the grade overview at AZ91C.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution heat treated and naturally aged | Choose for maximum ductility and impact toughness in cast magnesium parts, at the cost of low yield strength. | 90 | 275 | 14 | 55 HB | 68 W/m·K |
FDefault As fabricated | Default foundry condition: lowest cost, adequate for lightly loaded housings and covers where no heat treatment is justified. | 97 | 165 | 2.5 | 60 HB | 72 W/m·K |
Cooled from hot working and artificially aged | Low-cost stabilizing age used to raise yield strength and dimensional stability slightly without a full solution cycle. | 110 | 165 | 2 | 65 HB | — |
T6This page Solution heat treated and artificially aged | Highest-strength condition for structural sand/permanent-mold castings where yield strength and hardness matter more than ductility. | 145 | 275 | 6 | 70 HB | 72 W/m·K |
What is AZ91C-T6?
AZ91C-T6 is AZ91C in the T6 temper — highest-strength condition for structural sand/permanent-mold castings where yield strength and hardness matter more than ductility. AZ91C-T6 has a yield strength of 145 MPa (21 ksi) and a tensile strength of 275 MPa (39.9 ksi) — stronger than 51% of magnesium alloy grades. Elongation at break is 6% and the elastic modulus is 45 GPa (6.53 Msi). AZ91C-T6 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). F is the default condition FabDigit quotes; T6 is available on request or by drawing note.
Limitations
- Low fracture toughness — 12 MPa·√m (10.9 ksi·√in), worse than 92% 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
AZ91C-T6 properties
Typical room-temperature values for AZ91C-T6; 13 are specific to this condition. Other listed values are AZ91C reference data and may not represent this condition. Bars are the position among magnesium alloy grades.
Physical3
AZ91C-T6 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).
Mechanical13
AZ91C-T6 has a yield strength of 145 MPa (21 ksi) and a tensile strength of 275 MPa (39.9 ksi) — stronger than 51% of magnesium alloy grades. Elongation at break is 6% and the elastic modulus is 45 GPa (6.53 Msi).
Thermal6
AZ91C-T6 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
AZ91C-T6 conducts electricity at 12 % IACS, worse than 78% of magnesium alloy grades.
Chemical & Environmental3
Corrosion resistance is poor (20/100), worse than 77% of magnesium alloy grades.
Sustainability4
Producing a kilogram of AZ91C-T6 takes about 355 MJ of energy and emits 28 kg of CO₂ — more than 85% of magnesium alloy grades. Typical recycled content is 35%.
Manufacturability8
AZ91C-T6's machinability is excellent (95/100, better than 54% of magnesium alloy grades); weldability good (65/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with AZ91C-T6
Is AZ91C easy to machine?
Outstanding machinability — high speeds, low cutting forces, sharp positive-rake tools and dry or oil (never water-based) coolant; collect and control fine chips/dust because of fire risk.
Can AZ91C be welded?
Readily GTAW/GMAW welded in inert gas with AZ92A or AZ101A filler; preheat thin sections, avoid Zn-rich fillers on thick joints and stress relieve (~260 °C) to prevent SCC.
Can AZ91C be formed, bent or molded?
Casting alloy only — excellent sand and permanent-mold castability with SF6-free cover gas or flux; needs generous fillets and controlled solidification to avoid microporosity, and no cold forming.
What surface finishes work on AZ91C?
Not sulfuric-anodizable: apply chromate/fluoride or fluoride-free conversion coating, Dow 17/HAE or PEO, then epoxy primer and topcoat; insulate all steel/brass fasteners to avoid galvanic attack.
AZ91C 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 |
| Mn0.13 % min per ASTM B80 | ≥ 0.13 | 0.2 |
| Si | ≤ 0.3 | — |
| Cu | ≤ 0.1 | — |
| Ni | ≤ 0.01 | — |
| Others (total) | ≤ 0.3 | — |
| Mg | balance | — |
AZ91C-T6 — frequently asked
What is AZ91C-T6 used for?
AZ91C-T6 is typically used for sand-cast gearbox and machinery housings, permanent-mold pump bodies, instrument and avionics housings, prototype castings ahead of die-cast tooling, equipment brackets and covers and low-volume structural castings. In short: weldable AZ91 casting grade; sand and permanent-mold route; heat-treatable to T6.
What is the yield strength of AZ91C-T6?
AZ91C-T6 has a typical yield strength of 145 MPa (21 ksi) and a tensile strength of 275 MPa (39.9 ksi) — stronger than 51% of magnesium alloy grades. Strength varies by condition: see the 4 listed tempers.
Is AZ91C-T6 easy to machine?
Yes — machinability is rated excellent (95/100, better than 54% of magnesium alloy grades). Outstanding machinability — high speeds, low cutting forces, sharp positive-rake tools and dry or oil (never water-based) coolant; collect and control fine chips/dust because of fire risk.
Can AZ91C-T6 be welded?
Yes — weldability is rated good (65/100). Readily GTAW/GMAW welded in inert gas with AZ92A or AZ101A filler; preheat thin sections, avoid Zn-rich fillers on thick joints and stress relieve (~260 °C) to prevent SCC.
What surface finishes work on AZ91C-T6?
Not sulfuric-anodizable: apply chromate/fluoride or fluoride-free conversion coating, Dow 17/HAE or PEO, then epoxy primer and topcoat; insulate all steel/brass fasteners to avoid galvanic attack.
Can AZ91C-T6 be formed, bent or molded?
Casting alloy only — excellent sand and permanent-mold castability with SF6-free cover gas or flux; needs generous fillets and controlled solidification to avoid microporosity, and no cold forming.
What is the maximum service temperature of AZ91C-T6?
AZ91C-T6 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 AZ91C-F and AZ91C-T6?
F is the default condition — default foundry condition: lowest cost, adequate for lightly loaded housings and covers where no heat treatment is justified. T6: highest-strength condition for structural sand/permanent-mold castings where yield strength and hardness matter more than ductility. Yield strength is 97 MPa in F versus 145 MPa in T6.
Sources
- ASTM B80 — Magnesium-Alloy Sand Castings — ASTM International (2015)
- ASTM B199 — Magnesium-Alloy Permanent Mold Castings — ASTM International (2019)
- ASTM B661 — Heat Treatment of Magnesium Alloys — ASTM International (2019)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys (Magnesium) — ASM International (1990)
- ASM Handbook Vol. 15 — Casting (Magnesium Foundry Practice) — ASM International (2008)
- ASM Specialty Handbook: Magnesium and Magnesium Alloys — ASM International (1999)
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.