Magnesium Alloy HK31A · temper
Magnesium Alloy HK31A-T6
Properties of the T6 condition, compared with the other HK31A tempers.
Cast HK31A per ASTM B80 for elevated-temperature housings and covers where creep resistance to ~350 °C matters more than absolute strength.
What is HK31A-T6?
HK31A-T6 is HK31A in the T6 temper — cast HK31A per ASTM B80 for elevated-temperature housings and covers where creep resistance to ~350 °C matters more than absolute strength. HK31A-T6 has a yield strength of 105 MPa (15.2 ksi) and a tensile strength of 220 MPa (31.9 ksi) — weaker than 87% of magnesium alloy grades. Elongation at break is 8% and the elastic modulus is 45 GPa (6.53 Msi). HK31A-T6 has a density of 1.79 g/cm³ (0.0647 lb/in³), lighter than 73% of magnesium alloy grades. It melts at 588°C (1,090 °F). H24 is the default condition FabDigit quotes; T6 is available on request or by drawing note.
Advantages
- High service temperature — 350°C (662 °F), better than 101% of magnesium alloy grades
- Forms and bends easily — 35/100, better than 87% of magnesium alloy grades
- High electrical conductivity — 28 % IACS, better than 85% of magnesium alloy grades
Limitations
- Low strength — 105 MPa (15.2 ksi), worse than 87% of magnesium alloy grades
HK31A-T6 properties
Typical room-temperature values for HK31A-T6 — 12 properties are specific to this condition; the rest are grade-level values shared by every HK31A temper. Each bar shows where the value sits among the magnesium alloy grades in FabDigit's library — further right is higher.
Physical3
HK31A-T6 has a density of 1.79 g/cm³ (0.0647 lb/in³), lighter than 73% of magnesium alloy grades. It melts at 588°C (1,090 °F).
Mechanical11
HK31A-T6 has a yield strength of 105 MPa (15.2 ksi) and a tensile strength of 220 MPa (31.9 ksi) — weaker than 87% of magnesium alloy grades. Elongation at break is 8% and the elastic modulus is 45 GPa (6.53 Msi).
Thermal6
HK31A-T6 is rated for continuous service to 350°C (662 °F). It conducts heat at 92 W/m·K (53.2 BTU/hr·ft·°F), worse than 52% of magnesium alloy grades. Thermal expansion is 26.1 µm/m·K (14.5 µin/in·°F).
Electrical3
HK31A-T6 conducts electricity at 28 % IACS, better than 85% of magnesium alloy grades.
Chemical & Environmental3
Corrosion resistance is poor (20/100), worse than 77% of magnesium alloy grades.
Sustainability4
Producing a kilogram of HK31A-T6 takes about 350 MJ of energy and emits 32 kg of CO₂ — more than 74% of magnesium alloy grades. Typical recycled content is 5%.
Manufacturability8
HK31A-T6's machinability is excellent (95/100, better than 54% of magnesium alloy grades); weldability very good (70/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other HK31A tempers and conditions
HK31A is also supplied in 3 other conditions. The full side-by-side table is on the HK31A overview.
- H24DefaultStandard supply condition for HK31A sheet and plate; best strength/creep combination for hot structures to ~315 °C.200 MPa yield · 57 HB
- OChoose when maximum ductility for warm forming/deep drawing is needed; strength then restored partly by post-form stress relief.140 MPa yield · 45 HB
- T6Cast HK31A per ASTM B80 for elevated-temperature housings and covers where creep resistance to ~350 °C matters more than absolute strength.105 MPa yield · 55 HB
Working with HK31A-T6
Is HK31A easy to machine?
Machines extremely easily at high speed with sharp tools and generous rake, but fine chips are flammable — no water-based coolant, keep chips dry, ground and swept up; thorium content requires dust/swarf controlled as radioactive material.
Can HK31A be welded?
GTAW/GMAW in argon with HK31A or EZ33A filler gives good joints; preheat 150–260 °C for thick sections and stress relieve after welding to limit SCC and distortion.
Can HK31A be formed, bent or molded?
Form warm at 230–320 °C (O temper preferred); cold bending is limited to generous radii because of the hcp structure — sand castings are poured in dry sand with SF6-free inhibited cover gas.
What surface finishes work on HK31A?
Chemical conversion coating (chrome-free or Dow 7) or HAE/Dow 17 anodizing followed by epoxy primer and topcoat is mandatory; isolate from steel, copper and carbon-fibre parts to avoid galvanic attack.
HK31A 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 |
|---|---|---|
| Thradioactive alloying addition; source-material controls apply | 2.5 – 4 | 3.25 |
| Zrgrain refiner | 0.4 – 1 | 0.7 |
| Cuimpurity limit | ≤ 0.1 | — |
| Niimpurity limit, corrosion critical | ≤ 0.01 | — |
| Feimpurity limit | ≤ 0.01 | — |
| Others (each)total others 0.30 max | ≤ 0.05 | — |
| Mg | balance | — |
HK31A-T6 — frequently asked
What is HK31A-T6 used for?
HK31A-T6 is typically used for aerospace heat-shield panels, elevated-temperature structural skins, engine fittings, missile and airframe sheet components, high-temperature sand castings and ducting and shroud panels. In short: heat-resistant magnesium plate.
What is the yield strength of HK31A-T6?
HK31A-T6 has a typical yield strength of 105 MPa (15.2 ksi) and a tensile strength of 220 MPa (31.9 ksi) — weaker than 87% of magnesium alloy grades. Strength varies by condition: see the 4 listed tempers.
Is HK31A-T6 easy to machine?
Yes — machinability is rated excellent (95/100, better than 54% of magnesium alloy grades). Machines extremely easily at high speed with sharp tools and generous rake, but fine chips are flammable — no water-based coolant, keep chips dry, ground and swept up; thorium content requires dust/swarf controlled as radioactive material.
Can HK31A-T6 be welded?
Yes — weldability is rated very good (70/100). GTAW/GMAW in argon with HK31A or EZ33A filler gives good joints; preheat 150–260 °C for thick sections and stress relieve after welding to limit SCC and distortion.
What surface finishes work on HK31A-T6?
Chemical conversion coating (chrome-free or Dow 7) or HAE/Dow 17 anodizing followed by epoxy primer and topcoat is mandatory; isolate from steel, copper and carbon-fibre parts to avoid galvanic attack.
Can HK31A-T6 be formed, bent or molded?
Form warm at 230–320 °C (O temper preferred); cold bending is limited to generous radii because of the hcp structure — sand castings are poured in dry sand with SF6-free inhibited cover gas.
What is the maximum service temperature of HK31A-T6?
HK31A-T6 is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between HK31A-H24 and HK31A-F?
H24 is the default condition — standard supply condition for HK31A sheet and plate; best strength/creep combination for hot structures to ~315 °C. F: as-cast condition used only for non-critical parts or as the starting state before T6 solution/aging. Yield strength is 200 MPa in H24 versus 95 MPa in F.
Can FabDigit make parts in HK31A-T6?
Yes — HK31A-T6 is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM B90/B90M — Magnesium-Alloy Sheet and Plate — ASTM International (2021)
- ASTM B80 — Magnesium-Alloy Sand Castings — ASTM International (2015)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Specialty Handbook: Magnesium and Magnesium Alloys — ASM International (1999)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
- MMPDS / MIL-HDBK-5 magnesium sheet allowables — FAA/Battelle (2019)
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.