Magnesium Alloy AZ91D vs ZK51A
Magnesium Alloy · grade comparison
Magnesium Alloy AZ91D and ZK51A are both magnesium alloy grades. AZ91D is the stronger of the two: tensile strength 230 MPa (33.4 ksi) against 205 MPa (29.7 ksi) for ZK51A, about 12% more. In exchange, ZK51A is the more ductile: elongation 3.5% versus 3% for AZ91D. ZK51A conducts heat better (109 W/m·K vs 72 W/m·K). On the shop floor, AZ91D welds better (fair vs poor) and AZ91D sits in a lower cost tier (standard, $$) than ZK51A (premium, $$$).
AZ91DChoose it when strength drives the design, or when it will be welded.
ZK51AChoose it when the part is bent, formed or impact-loaded.
AZ91D vs ZK51A: 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.
Shear Modulus
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 45 GPa6.5 Msi · Bulk Modulus 45 GPa6.5 Msi · Poisson's Ratio 0.35
Physical
Density and transition temperatures.
Melting Point (Solidus)
Liquidus Temperature
Same in both: Density 1.81 g/cm³0.07 lb/in³
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Latent Heat of Fusion
Min Service Temperature
Same in both: Max Service Temperature (continuous) 120°C248 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Galvanic Potential (seawater, vs SCE)
Corrosion Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Castability
Brazeability / Solderability
Same in both: Machinability 98 / 100 · Polishability 55 / 100
Sustainability
Primary-production footprint per kilogram.
Typical Recycled Content
Same in both: Embodied Energy (primary production) 320 MJ/kg137,575 BTU/lb · Embodied Carbon (primary production) 32 kg CO₂/kg · Embodied Water 500 L/kg59.9 gal/lb
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Modulus of Resilience
Thermal Diffusivity
Thermal Shock Resistance Index
Same in both: Specific Stiffness (E / density) 24.9 MN·m/kg
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 | AZ91D | ZK51A |
|---|---|---|
| CNC machining | Yes | — |
| Casting & forging | Yes | — |
| Default condition | As Cast | — |
| Relative cost | $$ Standard | $$$ Premium |
| 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 | — |
AZ91D vs ZK51A — frequently asked
Is AZ91D stronger than ZK51A?
Yes. AZ91D has a typical tensile strength of 230 MPa (33.4 ksi) against 205 MPa (29.7 ksi) for ZK51A — about 12% more.
Which is cheaper, AZ91D or ZK51A?
AZ91D is the lower-cost material: it sits in the standard tier ($$) while ZK51A is premium ($$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which welds better, AZ91D or ZK51A?
AZ91D. Its weldability rates fair (40/100) against poor (15/100) for ZK51A.
Ready to make it?
Upload a CAD file and FabDigit prices the part in AZ91D and ZK51A 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.