Aluminum 4145
AA 4145 · UNS A94145 · EN AW-4145, AW 4145
4145 is an Al-10Si-4Cu filler alloy (EN AW-4145, AlSi10Cu4) supplied as welding wire (ER4145), aluminium brazing filler (AWS BAlSi-3) and, in smaller volumes, as cladding on brazing sheet.
4145 tempers and conditions
4145 is supplied in one standard condition, T6.
What is 4145?
4145 is an Al-10Si-4Cu filler alloy (EN AW-4145, AlSi10Cu4) supplied as welding wire (ER4145), aluminium brazing filler (AWS BAlSi-3) and, in smaller volumes, as cladding on brazing sheet. The high silicon gives a wide melting range, good fluidity and low hot-cracking tendency, while 4 % copper lets the deposit strengthen through post-weld solution treatment and artificial ageing (T6), making it the usual filler for copper-bearing 2000-series alloys and 206/319/354/380 castings. Copper degrades corrosion resistance and anodized appearance, ductility is low, and it must not be used on high-Mg 5000-series base metal. 4043 is the alternative where anodizing matters. 4145 has a density of 2.75 g/cm³ (0.0994 lb/in³), heavier than 67% of aluminum grades. It melts at 516°C (961 °F). 4145 has a yield strength of 110 MPa (16 ksi) and a tensile strength of 205 MPa (29.7 ksi) — weaker than 81% of aluminum grades. Elongation at break is 8% and the elastic modulus is 72 GPa (10.4 Msi).
What is 4145 used for?
- Casting repair welds
- Weld repair of 206/319/354/380 castings
- Welding of copper-bearing 2000-series alloys
- Aluminium brazing filler (BAlSi-3)
- Cladding layer on brazing sheet
- Salvage welding of aluminium tooling
Limitations
- Hard to polish — 35/100, worse than 98% of aluminum grades
- Low strength — 110 MPa (16 ksi), worse than 81% of aluminum grades
4145 properties
Typical room-temperature values; bars are the position among aluminum grades.
Physical3
4145 has a density of 2.75 g/cm³ (0.0994 lb/in³), heavier than 67% of aluminum grades. It melts at 516°C (961 °F).
Mechanical10
4145 has a yield strength of 110 MPa (16 ksi) and a tensile strength of 205 MPa (29.7 ksi) — weaker than 81% of aluminum grades. Elongation at break is 8% and the elastic modulus is 72 GPa (10.4 Msi).
Thermal5
4145 is rated for continuous service to 150°C (302 °F). It conducts heat at 130 W/m·K (75.1 BTU/hr·ft·°F), worse than 65% of aluminum grades. Thermal expansion is 20.7 µm/m·K (11.5 µin/in·°F).
Electrical3
4145 conducts electricity at 31 % IACS, worse than 68% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 62% of aluminum grades.
Sustainability4
Producing a kilogram of 4145 takes about 200 MJ of energy and emits 12 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 15%.
Manufacturability8
4145's machinability is fair (45/100, worse than 72% of aluminum grades); weldability fair (45/100); formability poor (25/100).
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. 4145 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4145
Is 4145 easy to machine?
Machinable but the hard primary/eutectic Si abrades tooling — use polished-flute carbide or PCD, high speed, low feed and flood coolant.
Can 4145 be welded?
This is the filler itself: preferred for GTAW/GMAW repair of Cu-bearing 2000 series and 206/319/354/380 castings; do not use on high-Mg 5000-series base metal, and expect low ductility in the deposit.
Can 4145 be formed, bent or molded?
Not a forming alloy — supplied as drawn wire, rod, paste or braze cladding; cold forming of the deposit will crack it.
Manufacturability
The process limits FabDigit applies to 4145. Every 4145 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Good45 / 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 |
Sheet metal
| Formability | Better25 / 100 |
|---|---|
| Weldability | Excellent45 / 100 |
4145 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 |
|---|---|---|
| Si | 9.3 – 10.7 | 10 |
| Cu | 3.3 – 4.7 | 4 |
| Fe | ≤ 0.8 | |
| Mn | ≤ 0.15 | |
| Mg | ≤ 0.15 | |
| Cr | ≤ 0.15 | |
| Zn | ≤ 0.2 | |
| Others (each)0.15 total | ≤ 0.05 | |
| Al | balance |
What surface finishes work on 4145?
Anodizing is poor (dark, mottled); use chemical conversion coating plus paint, or accept a machined/as-welded surface. Polishing tends to reveal Si particles.
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 4145 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- A94145
- Aluminum Association
- AA4145
- EN / DIN / Werkstoff-Nr.
- AW-4145AW 4145AlSi10Cu4
- Also called
- BAlSi-3
How much does 4145 cost?
4145 is a standard-cost aluminum ($$), cheaper than about 80% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
4145 — frequently asked
What is 4145 used for?
4145 is typically used for casting repair welds, weld repair of 206/319/354/380 castings, welding of copper-bearing 2000-series alloys, aluminium brazing filler (BAlSi-3), cladding layer on brazing sheet and salvage welding of aluminium tooling. In short: cu-Si filler for cast aluminum welding.
What is the yield strength of 4145?
4145 has a typical yield strength of 110 MPa (16 ksi) and a tensile strength of 205 MPa (29.7 ksi) — weaker than 81% of aluminum grades.
Is 4145 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 72% of aluminum grades). Machinable but the hard primary/eutectic Si abrades tooling — use polished-flute carbide or PCD, high speed, low feed and flood coolant.
Can 4145 be welded?
With care — weldability is rated fair (45/100). This is the filler itself: preferred for GTAW/GMAW repair of Cu-bearing 2000 series and 206/319/354/380 castings; do not use on high-Mg 5000-series base metal, and expect low ductility in the deposit.
What surface finishes work on 4145?
Anodizing is poor (dark, mottled); use chemical conversion coating plus paint, or accept a machined/as-welded surface. Polishing tends to reveal Si particles.
Can 4145 be formed, bent or molded?
Not a forming alloy — supplied as drawn wire, rod, paste or braze cladding; cold forming of the deposit will crack it.
What is the maximum service temperature of 4145?
4145 is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 4145 cost?
4145 is a standard-cost aluminum ($$), cheaper than about 80% 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 4145?
Yes — 4145 is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- AWS A5.10/A5.10M — Welding Consumables, Aluminium and Aluminium-Alloy Rods and Electrodes — AWS (2021)
- AWS A5.8/A5.8M — Filler Metals for Brazing and Braze Welding (BAlSi-3) — AWS (2019)
- International Alloy Designations and Chemical Composition Limits for Wrought Aluminum (Teal Sheets) — The Aluminum Association (2018)
- EN ISO 18273 / EN 573-3 (EN AW-4145) — CEN (2019)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Handbook Vol. 13B — Corrosion: Materials — ASM International (2005)
- Aluminium filler metal ER4145 / 4145 braze rod datasheets — Various filler-metal producers (2023)
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.