Magnesium Alloy AZ91B vs AZ91D
Magnesium Alloy · grade comparison
Magnesium Alloy AZ91B and AZ91D are both magnesium alloy grades. AZ91D is the stronger of the two: yield strength 160 MPa (23.2 ksi) against 150 MPa (21.8 ksi) for AZ91B, about 7% more. AZ91D is harder — 75 HV against 70 HV for AZ91B — which matters for wear surfaces and threads. On the shop floor, AZ91D welds better (fair vs poor).
AZ91DChoose it when strength drives the design, or when surface hardness matters.
AZ91B vs AZ91D: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all magnesium alloy grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all magnesium alloy grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Yield Strength (0.2% offset)
Compressive Strength
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 45 GPa6.5 Msi · Shear Modulus 17 GPa2.5 Msi · Bulk Modulus 45 GPa6.5 Msi · Poisson's Ratio 0.35 · Tensile Strength (Ultimate) 230 MPa33.4 ksi · Elongation at Break 3% · Shear Strength 140 MPa20.3 ksi · Fatigue Strength (Endurance Limit) 97 MPa14.1 ksi · Fracture Toughness (K_IC) 13 MPa·√m11.8 ksi·√in · Charpy V-Notch Impact (RT) 2 J1.6 ft·lbf · Hardness, Brinell 63 HB
Physical
Density and transition temperatures.
Same in both: Density 1.81 g/cm³0.07 lb/in³ · Melting Point (Solidus) 470°C878 °F · Liquidus Temperature 595°C1,103 °F
Thermal
How each material carries heat and how hot it can run.
Latent Heat of Fusion
Min Service Temperature
Same in both: Thermal Conductivity 72 W/m·K41.6 BTU/hr·ft·°F · Specific Heat Capacity 1,020 J/kg·K0.24 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 26 µm/m·K14.4 µin/in·°F · Max Service Temperature (continuous) 120°C248 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Same in both: Electrical Resistivity 1.41×10⁻⁷ Ω·m5.55 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -1.55 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Weldability
Formability (cold)
Castability
Brazeability / Solderability
Same in both: Machinability Rating (AISI 1212 = 100 %) 400% · Polishability 55 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Typical Recycled Content
Same in both: Embodied Water 500 L/kg59.9 gal/lb
Common Calculations
Ratios derived from the values above.
Modulus of Resilience
Same in both: Specific Strength (UTS / density) 127 kN·m/kg · Specific Stiffness (E / density) 24.9 MN·m/kg · Thermal Diffusivity 39 mm²/s · Thermal Shock Resistance Index 14
Strength versus weight
Yield strength against density for every magnesium alloy grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | AZ91B | AZ91D |
|---|---|---|
| CNC machining | — | Yes |
| Casting & forging | — | Yes |
| Default condition | — | As Cast |
| Relative cost | $$ Standard | $$ Standard |
| Min. machined wall | — | 0.8 mm |
| Best machined surface | — | Ra 0.8 µm |
| Anodizing Type II | — | Yes |
| Chem Film (Alodine) | — | Yes |
| E-Coating | — | Yes |
| Hard Anodize Type III w/ PTFE | — | Yes |
| Hard Anodizing Type III | — | Yes |
| Painting | — | Yes |
| Powder Coating | — | Yes |
AZ91B vs AZ91D — frequently asked
Is AZ91D stronger than AZ91B?
Yes. AZ91D has a typical yield strength of 160 MPa (23.2 ksi) against 150 MPa (21.8 ksi) for AZ91B — about 7% more. Tensile strength is 230 MPa (33.4 ksi) vs 230 MPa (33.4 ksi).
Which is cheaper, AZ91B or AZ91D?
Both sit in the same relative cost tier ($$, standard); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which welds better, AZ91B or AZ91D?
AZ91D. Its weldability rates fair (40/100) against poor (30/100) for AZ91B.
Ready to make it?
Upload a CAD file and FabDigit prices the part in AZ91B and AZ91D side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.