Aluminum LM25 · heat-treated state
Aluminum LM25-TB7
Properties of the TB7 condition, compared with the other LM25 tempers.
Dimensionally stable, ductile condition for castings that will see elevated temperature or need stress relief before precision machining.
What is LM25-TB7?
LM25-TB7 is LM25 heat treated to TB7 — dimensionally stable, ductile condition for castings that will see elevated temperature or need stress relief before precision machining. LM25-TB7 has a yield strength of 105 MPa (15.2 ksi) and a tensile strength of 180 MPa (26.1 ksi) — weaker than 84% of aluminum grades. Elongation at break is 4% and the elastic modulus is 71 GPa (10.3 Msi). LM25-TB7 has a density of 2.68 g/cm³ (0.0968 lb/in³), lighter than 72% of aluminum grades. It melts at 555°C (1,031 °F). T6 is the default condition FabDigit quotes; TB7 is available on request or by drawing note.
Advantages
- High service temperature — 200°C (392 °F), better than 90% of aluminum grades
- High electrical conductivity — 41 % IACS, better than 78% of aluminum grades
Limitations
- Low strength — 105 MPa (15.2 ksi), worse than 84% of aluminum grades
- Limited formability — 10/100, worse than 81% of aluminum grades
- Hard to polish — 45/100, worse than 76% of aluminum grades
LM25-TB7 properties
Typical room-temperature values for LM25-TB7 — 10 properties are specific to this condition; the rest are grade-level values shared by every LM25 temper. Each bar shows where the value sits among the aluminum grades in FabDigit's library — further right is higher.
Physical3
LM25-TB7 has a density of 2.68 g/cm³ (0.0968 lb/in³), lighter than 72% of aluminum grades. It melts at 555°C (1,031 °F).
Mechanical13
LM25-TB7 has a yield strength of 105 MPa (15.2 ksi) and a tensile strength of 180 MPa (26.1 ksi) — weaker than 84% of aluminum grades. Elongation at break is 4% and the elastic modulus is 71 GPa (10.3 Msi).
Thermal6
LM25-TB7 is rated for continuous service to 200°C (392 °F). It conducts heat at 158 W/m·K (91.3 BTU/hr·ft·°F), better than 73% of aluminum grades. Thermal expansion is 22 µm/m·K (12.2 µin/in·°F).
Electrical3
LM25-TB7 conducts electricity at 41 % IACS, better than 78% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is good (65/100), better than 71% of aluminum grades.
Sustainability4
Producing a kilogram of LM25-TB7 takes about 190 MJ of energy and emits 12 kg of CO₂ — less than 89% of aluminum grades. Typical recycled content is 50%.
Manufacturability8
LM25-TB7's machinability is good (58/100, worse than 53% of aluminum grades); weldability very good (75/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other LM25 tempers and conditions
LM25 is also supplied in 4 other conditions. The full side-by-side table is on the LM25 overview.
- T6DefaultStandard structural condition: highest strength and hardness for wheels, suspension and pressure-tight housings.215 MPa yield · 95 HB
- TELow-distortion, low-cost strengthening (no quench) for parts that must hold tight dimensions after machining.135 MPa yield · 75 HB
- TBChoose when maximum ductility and impact resistance matter more than strength (e.g. crash or bolted-joint castings).110 MPa yield · 65 HB
- TB7Dimensionally stable, ductile condition for castings that will see elevated temperature or need stress relief before precision machining.105 MPa yield · 65 HB
- FCheapest condition for low-stress, leak-tight housings where dimensional stability after machining is not critical.85 MPa yield · 60 HB
Working with LM25-TB7
Is LM25 easy to machine?
Machines cleanly with polished-flute carbide or PCD tooling at high speed; eutectic silicon is abrasive, so use PCD for long runs and flood coolant to avoid built-up edge.
Can LM25 be welded?
Readily TIG/MIG welded with 4043 (or 4047) filler; weld before heat treatment or re-solution/age afterwards, since welding locally overages T6 material.
Can LM25 be formed, bent or molded?
Excellent fluidity and low hot-tearing for sand, gravity-die and low-pressure casting; feed heavy sections and Sr-modify plus grain-refine for full T6 ductility, and avoid heavy T6 quench distortion on thin frames.
What surface finishes work on LM25?
Takes chromate/anodic protective coatings and paint well; hard anodize gives a dark grey film because of the 7 % Si, and polishing leaves a slight silicon-particle haze.
LM25 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 | 6.5 – 7.5 | 7 |
| MgSr or Na modified in most foundries | 0.2 – 0.45 | 0.35 |
| Fe0.50 max sand cast; 0.60 max reported for some pressure-tight grades | ≤ 0.5 | 0.2 |
| Cu | ≤ 0.2 | 0.05 |
| Mn | ≤ 0.3 | 0.05 |
| Ni | ≤ 0.1 | — |
| Zn | ≤ 0.1 | — |
| Pb | ≤ 0.1 | — |
| Sn | ≤ 0.05 | — |
| Tigrain refiner (Al-Ti-B) | ≤ 0.2 | 0.12 |
| Others (each)total 0.15 max | ≤ 0.05 | — |
| Al | balance | — |
LM25-TB7 — frequently asked
What is LM25-TB7 used for?
LM25-TB7 is typically used for wheel rims, aerospace castings, intake manifolds, pump housings, instrument and avionics housings and thin-wall complex gearbox covers. In short: BS heat-treatable Al-Si-Mg cast; A356 equivalent.
What is the yield strength of LM25-TB7?
LM25-TB7 has a typical yield strength of 105 MPa (15.2 ksi) and a tensile strength of 180 MPa (26.1 ksi) — weaker than 84% of aluminum grades. Strength varies by condition: see the 5 listed tempers.
Is LM25-TB7 easy to machine?
Reasonably — machinability is rated good (58/100, worse than 53% of aluminum grades). Machines cleanly with polished-flute carbide or PCD tooling at high speed; eutectic silicon is abrasive, so use PCD for long runs and flood coolant to avoid built-up edge.
Can LM25-TB7 be welded?
Yes — weldability is rated very good (75/100). Readily TIG/MIG welded with 4043 (or 4047) filler; weld before heat treatment or re-solution/age afterwards, since welding locally overages T6 material.
What surface finishes work on LM25-TB7?
Takes chromate/anodic protective coatings and paint well; hard anodize gives a dark grey film because of the 7 % Si, and polishing leaves a slight silicon-particle haze.
Can LM25-TB7 be formed, bent or molded?
Excellent fluidity and low hot-tearing for sand, gravity-die and low-pressure casting; feed heavy sections and Sr-modify plus grain-refine for full T6 ductility, and avoid heavy T6 quench distortion on thin frames.
What is the maximum service temperature of LM25-TB7?
LM25-TB7 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 LM25-T6 and LM25-F?
T6 is the default condition — standard structural condition: highest strength and hardness for wheels, suspension and pressure-tight housings. F: cheapest condition for low-stress, leak-tight housings where dimensional stability after machining is not critical. Yield strength is 215 MPa in T6 versus 85 MPa in F.
Can FabDigit make parts in LM25-TB7?
Yes — LM25-TB7 is available for CNC machining with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- BS 1490 — Aluminium and aluminium alloy ingots and castings for general engineering purposes — BSI (1988)
- BS EN 1706 — Aluminium and aluminium alloys, castings (EN AC-42100 AlSi7Mg0,3) — CEN (2020)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys (A356 data) — ASM International (1990)
- ASM Handbook Vol. 19 — Fatigue and Fracture (cast Al-Si-Mg alloys) — ASM International (1996)
- GB/T 1173 — (ZL101A) — SAC (2013)
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.