Magnesium Alloy ZK51A-T6
Temper
ASTM ZK51A · UNS M16510
T6 = 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.
Values for the T6 condition
Other ZK51A tempers and conditions
ZK51A is listed in 3 conditions; see the grade overview at ZK51A.
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 |
T6This page 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-T6?
ZK51A-T6 is ZK51A in the T6 temper — 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. ZK51A-T6 has a yield strength of 175 MPa (25.4 ksi) and a tensile strength of 215 MPa (31.2 ksi) — stronger than 72% of magnesium alloy grades. Elongation at break is 4% and the elastic modulus is 45 GPa (6.53 Msi). ZK51A-T6 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). T5 is the default condition FabDigit quotes; T6 is available on request or by drawing note.
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-T6 properties
Typical room-temperature values for ZK51A-T6; 20 are specific to this condition. Other listed values are ZK51A reference data and may not represent this condition. Bars are the position among magnesium alloy grades.
Physical3
ZK51A-T6 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-T6 has a yield strength of 175 MPa (25.4 ksi) and a tensile strength of 215 MPa (31.2 ksi) — stronger than 72% of magnesium alloy grades. Elongation at break is 4% and the elastic modulus is 45 GPa (6.53 Msi).
Thermal6
ZK51A-T6 is rated for continuous service to 120°C (248 °F). It conducts heat at 110 W/m·K (63.6 BTU/hr·ft·°F), better than 66% of magnesium alloy grades. Thermal expansion is 27 µm/m·K (15 µin/in·°F).
Electrical3
ZK51A-T6 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-T6 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-T6's machinability is excellent (97/100, better than 92% of magnesium alloy grades); weldability poor (15/100); formability not recommended (8/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with ZK51A-T6
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.
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.
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 | — |
ZK51A-T6 — frequently asked
What is ZK51A-T6 used for?
ZK51A-T6 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-T6?
ZK51A-T6 has a typical yield strength of 175 MPa (25.4 ksi) and a tensile strength of 215 MPa (31.2 ksi) — stronger than 72% of magnesium alloy grades. Strength varies by condition: see the 3 listed tempers.
Is ZK51A-T6 easy to machine?
Yes — machinability is rated excellent (97/100, better than 92% 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-T6 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-T6?
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-T6 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-T6?
ZK51A-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 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.