Magnesium Alloy AS21-F (As fabricated)
Temper · default condition
ASTM AS21 · EN MC21310, MgAl2Si
Standard commercial condition: hot-chamber/cold-chamber HPDC parts used as cast, with rapid solidification giving fine Mg2Si for creep resistance to ~150 °C.
Values for the F condition
Other AS21 tempers and conditions
AS21 is listed in 2 conditions; see the grade overview at AS21.
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
F | Rare, prototype-oriented condition: slower cooling coarsens the Mg2Si eutectic, so strength, ductility and creep performance all fall below HPDC values. | 90 | 150 | 5 | 48 HB | 15 % IACS |
FDefaultThis page As fabricated | Standard commercial condition: hot-chamber/cold-chamber HPDC parts used as cast, with rapid solidification giving fine Mg2Si for creep resistance to ~150 °C. | 120 | 220 | 13 | 55 HB | 68 W/m·K |
What is AS21-F?
AS21-F is AS21 in the F temper — standard commercial condition: hot-chamber/cold-chamber HPDC parts used as cast, with rapid solidification giving fine Mg2Si for creep resistance to ~150 °C. AS21-F has a yield strength of 120 MPa (17.4 ksi) and a tensile strength of 220 MPa (31.9 ksi) — weaker than 77% of magnesium alloy grades. Elongation at break is 13% and the elastic modulus is 45 GPa (6.53 Msi). AS21-F has a density of 1.76 g/cm³ (0.0636 lb/in³), lighter than 94% of magnesium alloy grades. It melts at 565°C (1,049 °F).
Advantages
- Good corrosion resistance — 33/100, better than 99% of magnesium alloy grades
- Ductile — tolerates forming and impact — 13%, better than 80% of magnesium alloy grades
Limitations
- Hard to polish — 45/100, worse than 93% of magnesium alloy grades
- Poor heat conductor — 68 W/m·K (39.3 BTU/hr·ft·°F), worse than 81% of magnesium alloy grades
- Low strength — 120 MPa (17.4 ksi), worse than 77% of magnesium alloy grades
AS21-F properties
Typical room-temperature values for AS21-F; 12 are specific to this condition. Other listed values are AS21 reference data and may not represent this condition. Bars are the position among magnesium alloy grades.
Physical3
AS21-F has a density of 1.76 g/cm³ (0.0636 lb/in³), lighter than 94% of magnesium alloy grades. It melts at 565°C (1,049 °F).
Mechanical13
AS21-F has a yield strength of 120 MPa (17.4 ksi) and a tensile strength of 220 MPa (31.9 ksi) — weaker than 77% of magnesium alloy grades. Elongation at break is 13% and the elastic modulus is 45 GPa (6.53 Msi).
Thermal6
AS21-F is rated for continuous service to 150°C (302 °F). It conducts heat at 68 W/m·K (39.3 BTU/hr·ft·°F), worse than 81% of magnesium alloy grades. Thermal expansion is 26.1 µm/m·K (14.5 µin/in·°F).
Electrical3
AS21-F conducts electricity at 16 % IACS, worse than 54% of magnesium alloy grades.
Chemical & Environmental3
Corrosion resistance is poor (33/100), better than 99% of magnesium alloy grades.
Sustainability4
Producing a kilogram of AS21-F takes about 340 MJ of energy and emits 32 kg of CO₂ — more than 59% of magnesium alloy grades. Typical recycled content is 25%.
Manufacturability8
AS21-F's machinability is excellent (95/100, better than 54% of magnesium alloy grades); weldability good (55/100); 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 AS21-F
Is AS21 easy to machine?
Cuts extremely freely with sharp, high-rake carbide tools and high speeds; run dry or with mineral oil (never water-based) and manage fine chips/dust as a fire hazard.
Can AS21 be welded?
GTAW/GMAW with AZ61/AZ92 or matching Mg filler works on gravity castings; HPDC AS21 welds poorly due to entrapped gas porosity — prefer mechanical joining or FSW.
Can AS21 be formed, bent or molded?
HPDC alloy: pour ~680–700 °C with fast fill and high cooling rate to keep Mg2Si fine; Si reduces fluidity so avoid very thin ribs, and protect the melt with SF6-free cover gas (SO2/HFC-134a).
What surface finishes work on AS21?
Not anodizable in the aluminium sense — use chromate-free conversion coating (ASTM D1732), Dow 17/HAE or PEO, then epoxy e-coat/powder; isolate all steel and aluminium fasteners to prevent galvanic attack.
AS21 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 |
|---|---|---|
| Alkept low to suppress Mg17Al12, the phase that causes AZ91 creep | 1.4 – 2.5 | 2.2 |
| Siforms Chinese-script/fine Mg2Si for grain-boundary pinning | 0.7 – 1.2 | 1 |
| Mniron control for corrosion resistance | 0.2 – 0.6 | 0.4 |
| Zn | ≤ 0.25 | 0.1 |
| Cuhigh-purity limit | ≤ 0.01 | — |
| Nihigh-purity limit | ≤ 0 | — |
| Fehigh-purity limit, Fe/Mn ratio controlled | ≤ 0 | — |
| Others (each) | ≤ 0.01 | — |
| Mg | balance | — |
AS21-F — frequently asked
What is AS21-F used for?
AS21-F is typically used for engine covers, transmission housings and creep-resistant brackets. In short: creep-resistant Mg die casting; 150 °C service, above AZ91; lower fluidity than AZ91.
What is the yield strength of AS21-F?
AS21-F has a typical yield strength of 120 MPa (17.4 ksi) and a tensile strength of 220 MPa (31.9 ksi) — weaker than 77% of magnesium alloy grades. Strength varies by condition: see the 2 listed tempers.
Is AS21-F easy to machine?
Yes — machinability is rated excellent (95/100, better than 54% of magnesium alloy grades). Cuts extremely freely with sharp, high-rake carbide tools and high speeds; run dry or with mineral oil (never water-based) and manage fine chips/dust as a fire hazard.
Can AS21-F be welded?
Yes — weldability is rated good (55/100). GTAW/GMAW with AZ61/AZ92 or matching Mg filler works on gravity castings; HPDC AS21 welds poorly due to entrapped gas porosity — prefer mechanical joining or FSW.
What surface finishes work on AS21-F?
Not anodizable in the aluminium sense — use chromate-free conversion coating (ASTM D1732), Dow 17/HAE or PEO, then epoxy e-coat/powder; isolate all steel and aluminium fasteners to prevent galvanic attack.
Can AS21-F be formed, bent or molded?
HPDC alloy: pour ~680–700 °C with fast fill and high cooling rate to keep Mg2Si fine; Si reduces fluidity so avoid very thin ribs, and protect the melt with SF6-free cover gas (SO2/HFC-134a).
What is the maximum service temperature of AS21-F?
AS21-F is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between AS21-F and AS21 F-GRAV?
F is the default condition — standard commercial condition: hot-chamber/cold-chamber HPDC parts used as cast, with rapid solidification giving fine Mg2Si for creep resistance to ~150 °C. F-GRAV: rare, prototype-oriented condition: slower cooling coarsens the Mg2Si eutectic, so strength, ductility and creep performance all fall below HPDC values. Yield strength is 120 MPa in F versus 90 MPa in F-GRAV.
Sources
- ASTM B94 — Standard Specification for Magnesium-Alloy Die Castings — ASTM International (2018)
- ASM Specialty Handbook: Magnesium and Magnesium Alloys — ASM International (1999)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
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.