Magnesium Alloy ZK40A-T5
Temper · default condition
ASTM ZK40A · UNS M16400
T5 = cooled from hot working and artificially aged
Standard supplied condition (ASTM B80): a simple single-step age that raises yield strength and stabilises dimensions with no solution treatment or quench distortion.
Values for the T5 condition
Other ZK40A tempers and conditions
ZK40A is listed in 2 conditions; see the grade overview at ZK40A.
- F
- T5
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Pick for lightly loaded castings where the T5 age is not economical; lower yield strength but the best as-cast ductility. | 120 | 220 | 6 | 55 HB | 27 % IACS |
T5DefaultThis page Cooled from hot working and artificially aged | Standard supplied condition (ASTM B80): a simple single-step age that raises yield strength and stabilises dimensions with no solution treatment or quench distortion. | 145 | 250 | 5 | 65 HB | 117 W/m·K |
What is ZK40A-T5?
ZK40A-T5 is ZK40A in the T5 temper — standard supplied condition (ASTM B80): a simple single-step age that raises yield strength and stabilises dimensions with no solution treatment or quench distortion. ZK40A-T5 has a yield strength of 145 MPa (21 ksi) and a tensile strength of 250 MPa (36.3 ksi) — stronger than 51% of magnesium alloy grades. Elongation at break is 5% and the elastic modulus is 45 GPa (6.53 Msi). ZK40A-T5 has a density of 1.83 g/cm³ (0.0661 lb/in³), heavier than 81% of magnesium alloy grades. It melts at 550°C (1,022 °F).
Advantages
- High electrical conductivity — 29 % IACS, better than 91% of magnesium alloy grades
- Conducts heat well — 117 W/m·K (67.6 BTU/hr·ft·°F), better than 80% of magnesium alloy grades
Limitations
- Hard to polish — 45/100, worse than 93% of magnesium alloy grades
- Difficult to weld — 30/100, worse than 90% of magnesium alloy grades
- Limited service temperature — 120°C (248 °F), worse than 78% of magnesium alloy grades
ZK40A-T5 properties
Typical room-temperature values for ZK40A-T5; 10 are specific to this condition. Other listed values are ZK40A reference data and may not represent this condition. Bars are the position among magnesium alloy grades.
Physical3
ZK40A-T5 has a density of 1.83 g/cm³ (0.0661 lb/in³), heavier than 81% of magnesium alloy grades. It melts at 550°C (1,022 °F).
Mechanical13
ZK40A-T5 has a yield strength of 145 MPa (21 ksi) and a tensile strength of 250 MPa (36.3 ksi) — stronger than 51% of magnesium alloy grades. Elongation at break is 5% and the elastic modulus is 45 GPa (6.53 Msi).
Thermal6
ZK40A-T5 is rated for continuous service to 120°C (248 °F). It conducts heat at 117 W/m·K (67.6 BTU/hr·ft·°F), better than 80% of magnesium alloy grades. Thermal expansion is 27 µm/m·K (15 µin/in·°F).
Electrical3
ZK40A-T5 conducts electricity at 29 % IACS, better than 91% of magnesium alloy grades.
Chemical & Environmental3
Corrosion resistance is poor (20/100), worse than 77% of magnesium alloy grades.
Sustainability4
Producing a kilogram of ZK40A-T5 takes about 290 MJ of energy and emits 28 kg of CO₂ — less than 99% of magnesium alloy grades. Typical recycled content is 15%.
Manufacturability8
ZK40A-T5's machinability is excellent (95/100, better than 54% of magnesium alloy grades); weldability poor (30/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with ZK40A-T5
Is ZK40A easy to machine?
Outstanding machinability at high speeds with sharp positive-rake tools and low forces; keep chips dry and never allow fine swarf to accumulate — use flood mineral-oil coolant, never water-based.
Can ZK40A be welded?
Poor: the Zn-rich, RE-free chemistry is hot-crack sensitive, so GTAW repair with EZ33A/ZK filler must be preheated and stress-relieved, and welded structures are generally avoided.
Can ZK40A be formed, bent or molded?
Sand or permanent-mould casting with zirconium-bearing melt practice; hold pouring temperature and grain-refinement carefully, add generous risering because of hot-tear tendency and a fairly narrow freezing range.
What surface finishes work on ZK40A?
No sulfuric anodizing — use chromate-free or Dow 17/HAE conversion/anodic coatings, then epoxy primer and topcoat; isolate all steel and copper-alloy fasteners to avoid galvanic attack.
ZK40A 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 | 3.5 – 4.5 | 4 |
| Zrgrain refiner, 0.45 % minimum | 0.45 – 1 | 0.7 |
| Others (total)total impurities per ASTM B80 | ≤ 0.3 | — |
| Mg | balance | — |
ZK40A-T5 — frequently asked
What is ZK40A-T5 used for?
ZK40A-T5 is typically used for sand-cast structural brackets, aerospace fittings, lightly loaded equipment housings, instrument mounting plates, accessory and gearbox covers and weight-critical non-pressurised castings. In short: rare-earth-free Mg casting; ductile ZK-series grade; near-top magnesium machinability.
What is the yield strength of ZK40A-T5?
ZK40A-T5 has a typical yield strength of 145 MPa (21 ksi) and a tensile strength of 250 MPa (36.3 ksi) — stronger than 51% of magnesium alloy grades. Strength varies by condition: see the 2 listed tempers.
Is ZK40A-T5 easy to machine?
Yes — machinability is rated excellent (95/100, better than 54% of magnesium alloy grades). Outstanding machinability at high speeds with sharp positive-rake tools and low forces; keep chips dry and never allow fine swarf to accumulate — use flood mineral-oil coolant, never water-based.
Can ZK40A-T5 be welded?
Not readily — weldability is rated poor (30/100). Poor: the Zn-rich, RE-free chemistry is hot-crack sensitive, so GTAW repair with EZ33A/ZK filler must be preheated and stress-relieved, and welded structures are generally avoided.
What surface finishes work on ZK40A-T5?
No sulfuric anodizing — use chromate-free or Dow 17/HAE conversion/anodic coatings, then epoxy primer and topcoat; isolate all steel and copper-alloy fasteners to avoid galvanic attack.
Can ZK40A-T5 be formed, bent or molded?
Sand or permanent-mould casting with zirconium-bearing melt practice; hold pouring temperature and grain-refinement carefully, add generous risering because of hot-tear tendency and a fairly narrow freezing range.
What is the maximum service temperature of ZK40A-T5?
ZK40A-T5 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 ZK40A-T5 and ZK40A-F?
T5 is the default condition — standard supplied condition (ASTM B80): a simple single-step age that raises yield strength and stabilises dimensions with no solution treatment or quench distortion. F: pick for lightly loaded castings where the T5 age is not economical; lower yield strength but the best as-cast ductility. Yield strength is 145 MPa in T5 versus 120 MPa in F.
Sources
- ASTM B80 — Standard Specification for Magnesium-Alloy Sand Castings — ASTM (2020)
- SAE/UNS M16400 alloy designation listing — SAE International (2017)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Specialty Handbook: Magnesium and Magnesium Alloys — ASM International (1999)
- MatWeb cast magnesium alloy datasheets — MatWeb LLC (2024)
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.