Magnesium Alloy ZK51A
ASTM ZK51A · UNS M16510
ZK51A is a higher-zinc Mg-Zn-Zr sand and permanent-mould casting alloy (UNS M16510), grain refined with zirconium and free of rare-earth additions, with F, T5 and T6 conditions on file.
Reference datasheet — ZK51A 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 T5 condition
ZK51A tempers and conditions
ZK51A is supplied in 3 conditions, soft to hard. T5 is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Pick when dimensional stability of the raw casting matters more than strength, or as the starting point for later ageing. | 125 | 175 | 5 | 55 HB | 26 % IACS |
T5Default Cooled from hot working and artificially aged | Standard commercial condition for ZK51A: simple single-step age (~175 °C/10–16 h) that raises yield strength with minimal distortion risk. | 165 | 205 | 3.5 | 65 HB | 109 W/m·K |
Solution heat treated and artificially aged | Occasionally applied to thick sections for slightly higher strength; rarely specified for ZK51A because the T5 response is already near-peak and solution treating risks Zn segregation/burning. | 175 | 215 | 4 | 70 HB | 27 % IACS |
What is ZK51A?
ZK51A is a higher-zinc Mg-Zn-Zr sand and permanent-mould casting alloy (UNS M16510), grain refined with zirconium and free of rare-earth additions, with F, T5 and T6 conditions on file. It is specified where more strength than ZK40A is needed — 165 MPa yield, 205 MPa tensile, 3.5% elongation and 65 HB — with 109 W/m·K conductivity and a machinability score of 98. The trade-offs are a weldability score of 15 (effectively non-weldable), a 120 °C service ceiling and a mandatory conversion-coat-plus-paint system. ZK61A-T6 is the higher-strength alternative. ZK51A has a density of 1.81 g/cm³ (0.0654 lb/in³), heavier than 58% of magnesium alloy grades. It melts at 549°C (1,020 °F). ZK51A has a yield strength of 165 MPa (23.9 ksi) and a tensile strength of 205 MPa (29.7 ksi) — stronger than 67% of magnesium alloy grades. Elongation at break is 3.5% and the elastic modulus is 45 GPa (6.53 Msi).
What is ZK51A used for?
- Aerospace sand castings
- General engineering castings of moderate strength
- Airframe brackets and fittings
- Permanent-mould structural castings
- Instrument and equipment housings
- Weight-critical mounting plates
Advantages
- High electrical conductivity — 27 % IACS, better than 80% of magnesium alloy grades
Limitations
- Difficult to weld — 15/100, worse than 100% of magnesium alloy grades
- Limited service temperature — 120°C (248 °F), worse than 78% of magnesium alloy grades
ZK51A properties
Typical room-temperature values for ZK51A-T5; bars are the position among magnesium alloy grades.
Physical3
ZK51A has a density of 1.81 g/cm³ (0.0654 lb/in³), heavier than 58% of magnesium alloy grades. It melts at 549°C (1,020 °F).
Mechanical13
ZK51A has a yield strength of 165 MPa (23.9 ksi) and a tensile strength of 205 MPa (29.7 ksi) — stronger than 67% of magnesium alloy grades. Elongation at break is 3.5% and the elastic modulus is 45 GPa (6.53 Msi).
Thermal6
ZK51A is rated for continuous service to 120°C (248 °F). It conducts heat at 109 W/m·K (63 BTU/hr·ft·°F), better than 63% of magnesium alloy grades. Thermal expansion is 27 µm/m·K (15 µin/in·°F).
Electrical3
ZK51A conducts electricity at 27 % IACS, better than 80% of magnesium alloy grades.
Chemical & Environmental3
Corrosion resistance is poor (22/100), worse than 57% of magnesium alloy grades.
Sustainability4
Producing a kilogram of ZK51A takes about 320 MJ of energy and emits 32 kg of CO₂ — less than 74% of magnesium alloy grades. Typical recycled content is 20%.
Manufacturability8
ZK51A's machinability is excellent (98/100, better than 96% of magnesium alloy grades); weldability poor (15/100); 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. ZK51A is highlighted; hover a dot for its name, or open the interactive family chart.
Working with ZK51A
Is ZK51A easy to machine?
Cuts extremely fast with sharp positive-rake tools and high speeds; use dry or mineral-oil coolant (never water-based) and manage fine chips/dust as a fire hazard.
Can ZK51A be welded?
Generally regarded as non-weldable — Zn-rich, Zr-grain-refined Mg is highly hot-crack sensitive; repair by plug/insert or specialised low-heat GTAW with ZK filler only after qualification.
Can ZK51A be formed, bent or molded?
Sand or permanent-mold cast only with SF6/SO2-free cover-gas melt protection, tight Zr control (settling loses Zr), and generous risering to fight microporosity and hot tearing.
ZK51A 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 |
|---|---|---|
| Znprincipal strengthener | 3.6 – 5.5 | 4.6 |
| Zrgrain refiner, added as Zirmax/Zr master alloy | 0.5 – 1 | 0.7 |
| Cuimpurity limit | ≤ 0.1 | |
| Niimpurity limit (corrosion critical) | ≤ 0.01 | |
| Feimpurity limit (corrosion critical) | ≤ 0.05 | |
| Siimpurity limit | ≤ 0.05 | |
| Others (each)total others 0.30 max | ≤ 0.05 | |
| Mg | balance |
What surface finishes work on ZK51A?
Requires chromate/fluoride conversion coating or Dow 17 / HAE anodize plus epoxy primer; isolate from steel, copper and carbon-fibre parts to prevent galvanic attack.
Equivalent designations
Standards and trade names that resolve to Magnesium Alloy ZK51A in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- M16510
- ASTM
- ZK51A-T5
How much does ZK51A cost?
ZK51A is a premium-cost magnesium alloy ($$$), cheaper than about 51% 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.
ZK51A — frequently asked
What is ZK51A used for?
ZK51A is typically used for aerospace sand castings, general engineering castings of moderate strength, airframe brackets and fittings, permanent-mould structural castings, instrument and equipment housings and weight-critical mounting plates. In short: stronger than ZK40A; top-of-class machinability; effectively non-weldable casting.
What is the yield strength of ZK51A?
ZK51A has a typical yield strength of 165 MPa (23.9 ksi) and a tensile strength of 205 MPa (29.7 ksi) — stronger than 67% of magnesium alloy grades. Strength varies by condition: see the 3 listed tempers.
Is ZK51A easy to machine?
Yes — machinability is rated excellent (98/100, better than 96% of magnesium alloy grades). Cuts extremely fast with sharp positive-rake tools and high speeds; use dry or mineral-oil coolant (never water-based) and manage fine chips/dust as a fire hazard.
Can ZK51A be welded?
Not readily — weldability is rated poor (15/100). Generally regarded as non-weldable — Zn-rich, Zr-grain-refined Mg is highly hot-crack sensitive; repair by plug/insert or specialised low-heat GTAW with ZK filler only after qualification.
What surface finishes work on ZK51A?
Requires chromate/fluoride conversion coating or Dow 17 / HAE anodize plus epoxy primer; isolate from steel, copper and carbon-fibre parts to prevent galvanic attack.
Can ZK51A be formed, bent or molded?
Sand or permanent-mold cast only with SF6/SO2-free cover-gas melt protection, tight Zr control (settling loses Zr), and generous risering to fight microporosity and hot tearing.
What is the maximum service temperature of ZK51A?
ZK51A 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 ZK51A-T5 and ZK51A-F?
T5 is the default condition — standard commercial condition for ZK51A: simple single-step age (~175 °C/10–16 h) that raises yield strength with minimal distortion risk. F: pick when dimensional stability of the raw casting matters more than strength, or as the starting point for later ageing. Yield strength is 165 MPa in T5 versus 125 MPa in F.
How much does ZK51A cost?
ZK51A is a premium-cost magnesium alloy ($$$), cheaper than about 51% 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 B80 — Standard Specification for Magnesium-Alloy Sand Castings — ASTM International (2021)
- ASTM B275 — Codification of Certain Nonferrous Metals and Alloys, Cast and Wrought — ASTM International (2021)
- ASM Specialty Handbook: Magnesium and Magnesium Alloys — ASM International (1999)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
- ASM Handbook Vol.15 — Casting — ASM International (2008)
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.