Aluminum 390
AA 390 · UNS A03900 · EN AlSi17Cu4Mg · also SC174A
390 (A03900) is a hypereutectic Al-Si-Cu-Mg die-casting and permanent-mould alloy with roughly 17% Si, 4.5% Cu and 0.5% Mg, whose primary silicon particles give very high wear resistance, low thermal expansion (about 18 µm/m·K), a high elastic modulus (about 81 GPa) and good dimensional stability at temperature.
390 tempers and conditions
390 is supplied in 4 conditions, soft to hard.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Cooled from hot working and artificially aged | Low-distortion stabilising age used on permanent-mold A390 castings to raise hardness and dimensional stability without full solution treatment. | 200 | 200 | 1 | 110 HB | 27 % IACS |
As fabricated | Standard stocked condition for as-cast wear parts and engine blocks; highest as-cast strength comes from the die-cast (B390) route. | 241 | 279 | 1 | 120 HB | 27 % IACS |
Solution heat treated and overaged (stabilized) | Overaged/stabilised temper chosen when dimensional stability at elevated temperature matters more than peak strength (compressor and engine components). | 262 | 262 | 1 | 120 HB | 28 % IACS |
Solution heat treated and artificially aged | Maximum strength and hardness condition for permanent-mold/sand A390 wear parts; ductility remains essentially nil. | 310 | 310 | 1 | 145 HB | 25 % IACS |
What is 390?
390 (A03900) is a hypereutectic Al-Si-Cu-Mg die-casting and permanent-mould alloy with roughly 17% Si, 4.5% Cu and 0.5% Mg, whose primary silicon particles give very high wear resistance, low thermal expansion (about 18 µm/m·K), a high elastic modulus (about 81 GPa) and good dimensional stability at temperature. It is the standard choice for linerless aluminum engine blocks, pistons, compressor bodies and pump housings. Ductility is effectively absent (elongation ≤1%), toughness and fracture toughness are low, PCD or diamond tooling is needed, and the copper content reduces corrosion resistance and weldability. 390 has a density of 2.73 g/cm³ (0.0986 lb/in³), heavier than 61% of aluminum grades. It melts at 507°C (945 °F). 390 has a yield strength of 241 MPa (35 ksi) and a tensile strength of 279 MPa (40.5 ksi) — stronger than 64% of aluminum grades. Elongation at break is 1% and the elastic modulus is 81 GPa (11.7 Msi).
What is 390 used for?
- Cylinder blocks
- Compressor parts
- Pumps
Advantages
- Stiff — 81 GPa (11.7 Msi), better than 96% of aluminum grades
- High service temperature — 175°C (347 °F), better than 83% of aluminum grades
Limitations
- Limited formability — 3/100, worse than 100% of aluminum grades
- Limited ductility — 1%, worse than 95% of aluminum grades
- Difficult to machine — 28/100, worse than 94% of aluminum grades
- Low fracture toughness — 15 MPa·√m (13.7 ksi·√in), worse than 93% of aluminum grades
- Hard to polish — 40/100, worse than 91% of aluminum grades
390 properties
Typical room-temperature values; bars are the position among aluminum grades.
Physical3
390 has a density of 2.73 g/cm³ (0.0986 lb/in³), heavier than 61% of aluminum grades. It melts at 507°C (945 °F).
Mechanical12
390 has a yield strength of 241 MPa (35 ksi) and a tensile strength of 279 MPa (40.5 ksi) — stronger than 64% of aluminum grades. Elongation at break is 1% and the elastic modulus is 81 GPa (11.7 Msi).
Thermal6
390 is rated for continuous service to 175°C (347 °F). It conducts heat at 134 W/m·K (77.4 BTU/hr·ft·°F), worse than 60% of aluminum grades. Thermal expansion is 18 µm/m·K (10 µin/in·°F).
Electrical3
390 conducts electricity at 27 % IACS, worse than 86% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (42/100), worse than 69% of aluminum grades.
Sustainability4
Producing a kilogram of 390 takes about 200 MJ of energy and emits 12 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 70%.
Manufacturability8
390's machinability is poor (28/100, worse than 94% of aluminum grades); weldability poor (22/100); formability not recommended (3/100).
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 aluminum family
Yield strength against density for every aluminum grade FabDigit runs. 390 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 390
Is 390 easy to machine?
Treat as an abrasive metal-matrix composite: PCD or diamond-coated tooling, high speed / light feed, flood coolant; carbide edges wear in minutes.
Can 390 be welded?
Poor — high Cu plus coarse primary Si makes it hot-crack sensitive; repair only by TIG with 4145/4047 filler and preheat, avoid structural welds.
Can 390 be formed, bent or molded?
Die casting (B390) or permanent-mold/sand casting only; needs superheat above ~760 °C and phosphorus refinement to keep primary Si fine, plus hardened tooling for melt handling.
Manufacturability
The process limits FabDigit applies to 390. Every 390 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Good28 / 100 |
|---|---|
| ISO material group | N.1 |
| Cutting speed (rough / finish) | 350 / 420 m/min |
| Minimum wall | 0.5 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 8× diameter |
| Best surface (machined / polished) | Ra 0.8 / — |
| Hardenable after machining | No |
390 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 |
|---|---|---|
| Siprimary silicon particles give the wear resistance and low CTE | 16 – 18 | 17 |
| Cu | 4 – 5 | 4.5 |
| Mg | 0.45 – 0.65 | 0.55 |
| FeA390.0 limits Fe to 0.50 max | ≤ 1.3 | |
| MnB390.0 allows 0.50 max | ≤ 0.1 | |
| ZnB390.0 allows 1.5 max | ≤ 0.1 | |
| Ti | ≤ 0.2 | |
| NiB390.0 | ≤ 0.1 | |
| SnB390.0 | ≤ 0.1 | |
| Others (each)total 0.20 max | ≤ 0.1 | |
| Al | balance |
What surface finishes work on 390?
Anodising is dull and patchy; typical practice is precision honing to expose silicon for bore wear surfaces, or chemical/organic coatings and mechanical plating for corrosion protection.
Surface treatments FabDigit runs on aluminum parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Passivation
Conversion Coating
PVD Coating
Equivalent designations
Standards and trade names that resolve to Aluminum 390 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- A03900
- EN / DIN / Werkstoff-Nr.
- AlSi17Cu4Mg
- Trade names
- SC174A
- Similar grades
- YL117
How much does 390 cost?
390 is a standard-cost aluminum ($$), cheaper than about 81% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
390 — frequently asked
What is 390 used for?
390 is typically used for cylinder blocks, compressor parts and pumps. In short: hypereutectic wear cast.
What is the yield strength of 390?
390 has a typical yield strength of 241 MPa (35 ksi) and a tensile strength of 279 MPa (40.5 ksi) — stronger than 64% of aluminum grades. Strength varies by condition: see the 4 listed tempers.
Is 390 easy to machine?
Not especially — machinability is rated poor (28/100, worse than 94% of aluminum grades). Treat as an abrasive metal-matrix composite: PCD or diamond-coated tooling, high speed / light feed, flood coolant; carbide edges wear in minutes.
Can 390 be welded?
Not readily — weldability is rated poor (22/100). Poor — high Cu plus coarse primary Si makes it hot-crack sensitive; repair only by TIG with 4145/4047 filler and preheat, avoid structural welds.
What surface finishes work on 390?
Anodising is dull and patchy; typical practice is precision honing to expose silicon for bore wear surfaces, or chemical/organic coatings and mechanical plating for corrosion protection.
Can 390 be formed, bent or molded?
Die casting (B390) or permanent-mold/sand casting only; needs superheat above ~760 °C and phosphorus refinement to keep primary Si fine, plus hardened tooling for melt handling.
What is the maximum service temperature of 390?
390 is rated for continuous use to about 175°C (347 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 390 cost?
390 is a standard-cost aluminum ($$), cheaper than about 81% 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.
Can FabDigit make parts in 390?
Yes — 390 is available for CNC machining; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM B85/B85M – Aluminum-Alloy Die Castings — ASTM International (2021)
- ASTM B108/B108M – Aluminum-Alloy Permanent Mold Castings — ASTM International (2019)
- Designations and Chemical Composition Limits for Aluminum Alloys in the Form of Castings and Ingot (Pink Sheets) — The Aluminum Association (2018)
- ASM Handbook Vol. 2 – Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Specialty Handbook: Aluminum and Aluminum Alloys — ASM International (1993)
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.