Aluminum ZL108-T7
Temper
GB ZL108 · JIS AC8A
T7 = solution heat treated and overaged (stabilized)
Overaged for maximum dimensional and structural stability in long-term hot service (250–300 °C), at some loss of room-temperature strength.
Values for the T7 condition
Other ZL108 tempers and conditions
ZL108 is listed in 5 conditions; see the grade overview at ZL108.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Pick for low-cost parts where dimensional stability at temperature and maximum strength are not required. | 130 | 175 | 1 | 80 HB | 30 % IACS |
Cooled from hot working and artificially aged | Short stabilising age used when quick throughput and stable dimensions matter more than peak strength. | 160 | 195 | 0.9 | 88 HB | 29 % IACS |
Cooled from hot working and naturally aged | Standard low-cost piston condition: aging only, good dimensional stability without the distortion risk of quenching. | 170 | 205 | 0.8 | 90 HB | 29 % IACS |
T7This page Solution heat treated and overaged (stabilized) | Overaged for maximum dimensional and structural stability in long-term hot service (250–300 °C), at some loss of room-temperature strength. | 185 | 225 | 1 | 95 HB | 30 % IACS |
T6Default Solution heat treated and artificially aged | Highest-strength, highest-hardness condition — the default choice for loaded pistons, compressor parts and wear surfaces. | 230 | 265 | 0.7 | 105 HB | 27 % IACS |
What is ZL108-T7?
ZL108-T7 is ZL108 in the T7 temper — overaged for maximum dimensional and structural stability in long-term hot service (250–300 °C), at some loss of room-temperature strength. ZL108-T7 has a yield strength of 185 MPa (26.8 ksi) and a tensile strength of 225 MPa (32.6 ksi) — weaker than 53% of aluminum grades. Elongation at break is 1% and the elastic modulus is 79 GPa (11.5 Msi). ZL108-T7 has a density of 2.68 g/cm³ (0.0968 lb/in³), lighter than 72% of aluminum grades. It melts at 516°C (961 °F). T6 is the default condition FabDigit quotes; T7 is available on request or by drawing note.
Advantages
- High service temperature — 300°C (572 °F), better than 99% of aluminum grades
Limitations
- Low fracture toughness — 14 MPa·√m (12.7 ksi·√in), worse than 97% of aluminum grades
- Limited ductility — 1%, worse than 95% of aluminum grades
- Limited formability — 5/100, worse than 94% of aluminum grades
- Hard to polish — 40/100, worse than 91% of aluminum grades
- Difficult to machine — 40/100, worse than 81% of aluminum grades
ZL108-T7 properties
Typical room-temperature values for ZL108-T7; 22 are specific to this condition. Other listed values are ZL108 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
ZL108-T7 has a density of 2.68 g/cm³ (0.0968 lb/in³), lighter than 72% of aluminum grades. It melts at 516°C (961 °F).
Mechanical12
ZL108-T7 has a yield strength of 185 MPa (26.8 ksi) and a tensile strength of 225 MPa (32.6 ksi) — weaker than 53% of aluminum grades. Elongation at break is 1% and the elastic modulus is 79 GPa (11.5 Msi).
Thermal6
ZL108-T7 is rated for continuous service to 300°C (572 °F). It conducts heat at 130 W/m·K (75.1 BTU/hr·ft·°F), worse than 65% of aluminum grades. Thermal expansion is 19.5 µm/m·K (10.8 µin/in·°F).
Electrical3
ZL108-T7 conducts electricity at 30 % IACS, worse than 73% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 62% of aluminum grades.
Sustainability4
Producing a kilogram of ZL108-T7 takes about 200 MJ of energy and emits 12 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 60%.
Manufacturability8
ZL108-T7's machinability is fair (40/100, worse than 81% of aluminum grades); weldability fair (40/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with ZL108-T7
Is ZL108 easy to machine?
Abrasive eutectic silicon demands PCD or diamond-coated carbide tooling, high speed/low feed and flood coolant; chips are short and finishing is good once tooling is right.
Can ZL108 be welded?
Repair-weldable by TIG with 4047/ZL102-type filler, but the 1–2 % Cu makes it hot-crack sensitive — preheat 150–200 °C and re-age after welding.
Can ZL108 be formed, bent or molded?
Gravity die (metal mould) casting is standard — excellent fluidity and low shrinkage; use P modification for the primary silicon, avoid Na, and feed heavy sections well since the alloy has essentially no cold formability.
What surface finishes work on ZL108?
Hard anodizing of crowns/ring grooves works well; decorative anodizing is dark and mottled, so paint, chemical conversion or Sn/graphite skirt coatings are the usual alternatives.
ZL108 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 |
|---|---|---|
| Sinear-eutectic; usually P-modified for primary Si refinement | 11 – 13 | 12 |
| Cu | 1 – 2 | 1.5 |
| Mg | 0.4 – 1 | 0.8 |
| Mn | 0.3 – 0.9 | 0.5 |
| Feimpurity limit, metal-mould castings | ≤ 0.8 | — |
| Znimpurity | ≤ 0.3 | — |
| Niimpurity | ≤ 0.3 | — |
| Tiimpurity / grain refiner residue | ≤ 0.2 | — |
| others (each)total ≤ 0.15 | ≤ 0.05 | — |
| Al | balance | — |
ZL108-T7 — frequently asked
What is ZL108-T7 used for?
ZL108-T7 is typically used for gasoline engine pistons, diesel engine piston blanks, reciprocating compressor pistons, air-conditioning compressor pistons, piston crowns and ring-belt sections and wear-resistant cast bushings and guides. In short: low-expansion piston alloy; wear-resistant eutectic Al-Si; stable to 250 °C.
What is the yield strength of ZL108-T7?
ZL108-T7 has a typical yield strength of 185 MPa (26.8 ksi) and a tensile strength of 225 MPa (32.6 ksi) — weaker than 53% of aluminum grades. Strength varies by condition: see the 5 listed tempers.
Is ZL108-T7 easy to machine?
Not especially — machinability is rated fair (40/100, worse than 81% of aluminum grades). Abrasive eutectic silicon demands PCD or diamond-coated carbide tooling, high speed/low feed and flood coolant; chips are short and finishing is good once tooling is right.
Can ZL108-T7 be welded?
With care — weldability is rated fair (40/100). Repair-weldable by TIG with 4047/ZL102-type filler, but the 1–2 % Cu makes it hot-crack sensitive — preheat 150–200 °C and re-age after welding.
What surface finishes work on ZL108-T7?
Hard anodizing of crowns/ring grooves works well; decorative anodizing is dark and mottled, so paint, chemical conversion or Sn/graphite skirt coatings are the usual alternatives.
Can ZL108-T7 be formed, bent or molded?
Gravity die (metal mould) casting is standard — excellent fluidity and low shrinkage; use P modification for the primary silicon, avoid Na, and feed heavy sections well since the alloy has essentially no cold formability.
What is the maximum service temperature of ZL108-T7?
ZL108-T7 is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between ZL108-T6 and ZL108-F?
T6 is the default condition — highest-strength, highest-hardness condition — the default choice for loaded pistons, compressor parts and wear surfaces. F: pick for low-cost parts where dimensional stability at temperature and maximum strength are not required. Yield strength is 230 MPa in T6 versus 130 MPa in F.
Sources
- GB/T 1173 (ZL108 / ZAlSi12Cu2Mg1) (2013)
- JIS H 5202 Aluminium alloy castings (AC8A) — JSA (2010)
- ASM Handbook Vol.2: Properties and Selection — Nonferrous Alloys (336.0) — ASM International (1990)
- ASM Specialty Handbook: Aluminum and Aluminum Alloys — ASM International (1993)
- Aluminum Association Pink Sheets — Designations and Chemical Composition Limits for Aluminum Alloys in the Form of Castings and Ingot — The Aluminum Association (2018)
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.