Magnesium Alloy AZ91B
ASTM AZ91B · UNS M11912
AZ91B is a wider-tolerance version of the AZ91 Mg-Al-Zn die-casting alloy (UNS M11912) that permits higher impurity levels to lower ingot cost.
Reference datasheet — AZ91B is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the F condition
AZ91B tempers and conditions
AZ91B is supplied in one standard condition, F. F is the default FabDigit quotes; the values on this page are for it.
Supply forms, finishes and certifications
Ways AZ91B is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
Ingot | Remelt die-casting ingot per ASTM B93 | Supply form |
What is AZ91B?
AZ91B is a wider-tolerance version of the AZ91 Mg-Al-Zn die-casting alloy (UNS M11912) that permits higher impurity levels to lower ingot cost. Mechanical performance in the F condition matches AZ91A — 150 MPa yield, 230 MPa tensile, 3% elongation, 63 HB and 72 W/m·K — and it is supplied as die castings and as remelt ingot. The relaxed Fe, Ni and Cu limits cut corrosion resistance to a score of 12, the lowest in the family, service is capped near 120 °C and weldability on die castings is poor (score 30). Specify AZ91D or AZ91E where salt-spray life matters. AZ91B 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). AZ91B has a yield strength of 150 MPa (21.8 ksi) and a tensile strength of 230 MPa (33.4 ksi) — stronger than 59% of magnesium alloy grades. Elongation at break is 3% and the elastic modulus is 45 GPa (6.53 Msi).
What is AZ91B used for?
- Cost-sensitive die-cast housings
- General die-cast components
- Consumer appliance frames
- Hand tool bodies
- Interior automotive brackets
- Remelt ingot for die-casting cells
Limitations
- Needs corrosion protection — 12/100, worse than 98% of magnesium alloy grades
- Difficult to weld — 30/100, worse than 90% of magnesium alloy grades
- Limited ductility — 3%, worse than 85% 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
AZ91B properties
Typical room-temperature values for AZ91B-F; bars are the position among magnesium alloy grades.
Physical3
AZ91B 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
AZ91B has a yield strength of 150 MPa (21.8 ksi) and a tensile strength of 230 MPa (33.4 ksi) — stronger than 59% of magnesium alloy grades. Elongation at break is 3% and the elastic modulus is 45 GPa (6.53 Msi).
Thermal6
AZ91B 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
AZ91B conducts electricity at 12 % IACS, worse than 78% of magnesium alloy grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 98% of magnesium alloy grades.
Sustainability4
Producing a kilogram of AZ91B takes about 310 MJ of energy and emits 30 kg of CO₂ — less than 85% of magnesium alloy grades. Typical recycled content is 40%.
Manufacturability8
AZ91B's machinability is excellent (95/100, better than 54% of magnesium alloy grades); weldability poor (30/100); formability not recommended (10/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the magnesium alloy family
Yield strength against density for every magnesium alloy grade FabDigit runs. AZ91B is highlighted; hover a dot for its name, or open the interactive family chart.
Working with AZ91B
Is AZ91B easy to machine?
Cuts extremely fast with high speeds, sharp positive-rake tools and light feeds; keep chips coarse and use dry or mineral-oil cutting — never water-based coolant — and manage fine-chip fire risk.
Can AZ91B be welded?
GTAW with AZ92A/AZ101A filler is possible on clean sections, but die-cast porosity usually blisters, so joining is normally mechanical or adhesive.
Can AZ91B be formed, bent or molded?
A hot-chamber high-pressure die-casting alloy with excellent fluidity and thin-wall fill; not cold formable, and thick sections need adequate venting and SF6-free cover-gas melt protection.
AZ91B 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 | 8.3 – 9.7 | 9 |
| Zn | 0.35 – 1 | 0.7 |
| Mn0.13 % min | 0.13 – 0.5 | 0.25 |
| Si | ≤ 0.5 | |
| Cuhigher than AZ91A/D — main difference | ≤ 0.35 | |
| Ni | ≤ 0.03 | |
| Fe | ≤ 0.03 | |
| Others (each)residual, each | ≤ 0.02 | |
| Mg | balance |
What surface finishes work on AZ91B?
Always apply a chromate/chrome-free conversion coat or Dow 17/HAE anodize plus paint or powder coat; isolate from steel and aluminium fasteners to avoid severe galvanic attack.
Equivalent designations
Standards and trade names that resolve to Magnesium Alloy AZ91B in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- M11912
- Also called
- AZ91B-F
How much does AZ91B cost?
AZ91B is a standard-cost magnesium alloy ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
AZ91B — frequently asked
What is AZ91B used for?
AZ91B is typically used for cost-sensitive die-cast housings, general die-cast components, consumer appliance frames, hand tool bodies, interior automotive brackets and remelt ingot for die-casting cells. In short: lowest-cost AZ91 variant; widest impurity tolerance; weakest corrosion performance.
What is the yield strength of AZ91B?
AZ91B has a typical yield strength of 150 MPa (21.8 ksi) and a tensile strength of 230 MPa (33.4 ksi) — stronger than 59% of magnesium alloy grades.
Is AZ91B easy to machine?
Yes — machinability is rated excellent (95/100, better than 54% of magnesium alloy grades). Cuts extremely fast with high speeds, sharp positive-rake tools and light feeds; keep chips coarse and use dry or mineral-oil cutting — never water-based coolant — and manage fine-chip fire risk.
Can AZ91B be welded?
Not readily — weldability is rated poor (30/100). GTAW with AZ92A/AZ101A filler is possible on clean sections, but die-cast porosity usually blisters, so joining is normally mechanical or adhesive.
What surface finishes work on AZ91B?
Always apply a chromate/chrome-free conversion coat or Dow 17/HAE anodize plus paint or powder coat; isolate from steel and aluminium fasteners to avoid severe galvanic attack.
Can AZ91B be formed, bent or molded?
A hot-chamber high-pressure die-casting alloy with excellent fluidity and thin-wall fill; not cold formable, and thick sections need adequate venting and SF6-free cover-gas melt protection.
What is the maximum service temperature of AZ91B?
AZ91B is rated for continuous use to about 120°C (248 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does AZ91B cost?
AZ91B is a standard-cost magnesium alloy ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM B93/B93M — Magnesium Alloys in Ingot Form for Sand, Permanent Mold and Die Castings — ASTM International (2020)
- ASTM B94 — Magnesium-Alloy Die Castings — ASTM International (2018)
- ASM Specialty Handbook: Magnesium and Magnesium Alloys — ASM International (1999)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- SAE J465 / UNS M11912 alloy designation — SAE International (2013)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.