Magnesium Alloy EQ21A
ASTM EQ21A · UNS M18330
EQ21A is a silver- and rare-earth-bearing magnesium casting alloy with zirconium grain refinement (UNS M18330), normally supplied in the T6 temper.
Reference datasheet — EQ21A 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 T6 condition
EQ21A tempers and conditions
EQ21A is supplied in 4 conditions, soft to hard. T6 is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Foundry intermediate state only; use when the casting will be solution treated later or for non-structural trial parts. | 100 | 175 | 5 | 55 HB | 23 % IACS |
Solution heat treated and naturally aged | Intermediate condition between solution treatment and ageing; slightly more ductile but well below T6 strength — rarely sold as a final condition. | 110 | 215 | 8 | 60 HB | 21 % IACS |
T6Default Solution heat treated and artificially aged | Standard supply condition for all EQ21A aerospace castings; maximum strength and best creep resistance to ~200 °C. | 195 | 260 | 4 | 80 HB | 113 W/m·K |
hot isostatically pressed then solution treated and aged | For flight-critical castings where residual microporosity must be closed; gives the best fatigue life and ductility scatter. | 195 | 270 | 6 | 82 HB | 25 % IACS |
What is EQ21A?
EQ21A is a silver- and rare-earth-bearing magnesium casting alloy with zirconium grain refinement (UNS M18330), normally supplied in the T6 temper. Engineers choose it for high strength combined with stable properties at elevated temperature: 195 MPa yield, 260 MPa tensile, 4 % elongation, 80 HB, 113 W/m·K thermal conductivity and service to 200 °C, in sand, investment and HIP+T6 cast aerospace parts. Corrosion resistance is poor (rated 25), so conversion or anodic coating plus galvanic isolation is mandatory, and the silver content makes it expensive and limited in availability. EZ33A or QE22 are the nearest alternatives where lower strength is acceptable. EQ21A has a density of 1.81 g/cm³ (0.0654 lb/in³), heavier than 58% of magnesium alloy grades. It melts at 550°C (1,022 °F). EQ21A has a yield strength of 195 MPa (28.3 ksi) and a tensile strength of 260 MPa (37.7 ksi) — stronger than 82% of magnesium alloy grades. Elongation at break is 4% and the elastic modulus is 44 GPa (6.38 Msi).
What is EQ21A used for?
- aerospace gearbox castings
- high-strength structural brackets
- racing component castings
Advantages
- Readily welded — 75/100, better than 91% of magnesium alloy grades
- Tough — resists crack growth — 16 MPa·√m (14.6 ksi·√in), better than 87% of magnesium alloy grades
- High service temperature — 200°C (392 °F), better than 84% of magnesium alloy grades
- High strength — 195 MPa (28.3 ksi), better than 82% of magnesium alloy grades
EQ21A properties
Typical room-temperature values for EQ21A-T6; bars are the position among magnesium alloy grades.
Physical3
EQ21A has a density of 1.81 g/cm³ (0.0654 lb/in³), heavier than 58% of magnesium alloy grades. It melts at 550°C (1,022 °F).
Mechanical14
EQ21A has a yield strength of 195 MPa (28.3 ksi) and a tensile strength of 260 MPa (37.7 ksi) — stronger than 82% of magnesium alloy grades. Elongation at break is 4% and the elastic modulus is 44 GPa (6.38 Msi).
Thermal6
EQ21A is rated for continuous service to 200°C (392 °F). It conducts heat at 113 W/m·K (65.3 BTU/hr·ft·°F), better than 74% of magnesium alloy grades. Thermal expansion is 26.7 µm/m·K (14.8 µin/in·°F).
Electrical3
EQ21A conducts electricity at 25 % IACS, better than 69% of magnesium alloy grades.
Chemical & Environmental3
Corrosion resistance is poor (25/100), better than 64% of magnesium alloy grades.
Sustainability4
Producing a kilogram of EQ21A takes about 350 MJ of energy and emits 32 kg of CO₂ — more than 74% of magnesium alloy grades. Typical recycled content is 15%.
Manufacturability8
EQ21A's machinability is excellent (92/100, worse than 86% of magnesium alloy grades); weldability very good (75/100); formability poor (15/100).
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. EQ21A is highlighted; hover a dot for its name, or open the interactive family chart.
Working with EQ21A
Is EQ21A easy to machine?
Machines extremely easily at high speed with sharp positive-rake tools and no coolant mist — but fine chips are pyrophoric, so keep dry, use flood mineral oil or dedicated chip handling and Class D extinguishers on hand.
Can EQ21A be welded?
Readily TIG/GTAW repair-welded with matching EQ21/QE22 filler under argon; weld local zones require re-solution + re-age (or local re-age) to restore T6 properties.
Can EQ21A be formed, bent or molded?
Casting alloy only — sand and investment cast with Zr-refined melt under SF6-free cover gas; not cold-formable, section design should promote directional solidification.
EQ21A 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 |
|---|---|---|
| Agsilver, provides age-hardening response with Nd | 1.3 – 1.7 | 1.5 |
| REneodymium-rich rare earth (didymium) | 1.5 – 3 | 2.1 |
| Zrgrain refiner | 0.4 – 1 | 0.7 |
| Cuintentional addition | 0.05 – 0.1 | 0.07 |
| Siimpurity limit | ≤ 0.01 | |
| Feimpurity limit | ≤ 0.01 | |
| Niimpurity limit, critical for corrosion | ≤ 0.01 | |
| Other, each | ≤ 0.01 | |
| Mg | balance |
What surface finishes work on EQ21A?
Chemical conversion coating (chromate-free Mg pretreatment) or anodic processes such as Dow 17/HAE/Tagnite, then epoxy primer and topcoat; insulate all steel/aluminium fastener interfaces to avoid galvanic attack.
Equivalent designations
Standards and trade names that resolve to Magnesium Alloy EQ21A in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- M18330
- ASTM
- EQ21A-T6
How much does EQ21A cost?
EQ21A is a high-cost magnesium alloy ($$$$), pricier than about 78% 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.
EQ21A — frequently asked
What is EQ21A used for?
EQ21A is typically used for aerospace gearbox castings, high-strength structural brackets and racing component castings. In short: highest-strength RE magnesium casting; stable to 200 °C; silver-bearing, high cost.
What is the yield strength of EQ21A?
EQ21A has a typical yield strength of 195 MPa (28.3 ksi) and a tensile strength of 260 MPa (37.7 ksi) — stronger than 82% of magnesium alloy grades. Strength varies by condition: see the 4 listed tempers.
Is EQ21A easy to machine?
Yes — machinability is rated excellent (92/100, worse than 86% of magnesium alloy grades). Machines extremely easily at high speed with sharp positive-rake tools and no coolant mist — but fine chips are pyrophoric, so keep dry, use flood mineral oil or dedicated chip handling and Class D extinguishers on hand.
Can EQ21A be welded?
Yes — weldability is rated very good (75/100). Readily TIG/GTAW repair-welded with matching EQ21/QE22 filler under argon; weld local zones require re-solution + re-age (or local re-age) to restore T6 properties.
What surface finishes work on EQ21A?
Chemical conversion coating (chromate-free Mg pretreatment) or anodic processes such as Dow 17/HAE/Tagnite, then epoxy primer and topcoat; insulate all steel/aluminium fastener interfaces to avoid galvanic attack.
Can EQ21A be formed, bent or molded?
Casting alloy only — sand and investment cast with Zr-refined melt under SF6-free cover gas; not cold-formable, section design should promote directional solidification.
What is the maximum service temperature of EQ21A?
EQ21A is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between EQ21A-T6 and EQ21A-F?
T6 is the default condition — standard supply condition for all EQ21A aerospace castings; maximum strength and best creep resistance to ~200 °C. F: foundry intermediate state only; use when the casting will be solution treated later or for non-structural trial parts. Yield strength is 195 MPa in T6 versus 100 MPa in F.
How much does EQ21A cost?
EQ21A is a high-cost magnesium alloy ($$$$), pricier than about 78% 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 — Magnesium-Alloy Sand Castings — ASTM International (2015)
- ASTM B199 — Magnesium-Alloy Permanent Mold Castings — ASTM International (2019)
- ASTM B403 — Magnesium-Alloy Investment Castings — ASTM International (2020)
- ASM Specialty Handbook: Magnesium and Magnesium Alloys — ASM International (1999)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- Elektron high-strength RE/Ag magnesium casting alloys — Magnesium Elektron (Luxfer MEL Technologies) (2019)
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.