Alloy basis

Silicon improves fluidity while magnesium enables precipitation hardening.

Typical applications

Automotive wheels, suspension components, pump housings, aerospace castings and general structural castings.

Common tempers / conditions

Common conditions include T6 and T7 heat-treated states.

Engineering selection notes

Confirm the exact alloy designation, temper, product form, thickness/diameter, mechanical properties, corrosion environment, joining process, surface treatment and certification. Properties can vary substantially by temper and product form.

QA/QC

For critical service, verify heat/lot traceability, mill certificate, chemical composition, tensile properties, temper, dimensional tolerances and any required NDT or third-party inspection.

Element Folio engineering reference. Verify the latest governing standard and producer data before design or procurement.

What engineers should check before specifying A356

A356 is a cast aluminium–silicon–magnesium alloy. Its usefulness depends on casting quality and the actual heat-treatment condition, not simply the alloy name. Sand casting, permanent-mould casting and other routes can produce different microstructures, porosity levels and mechanical performance. A drawing should therefore identify the casting process and acceptance requirements alongside the alloy and temper.

A356 versus 356 and wrought aluminium

A356 is commonly selected when a complex near-net-shape casting is required, while wrought alloys such as 6061 are more suitable for many extruded, rolled or machined shapes. The two cannot be substituted solely on the basis of nominal tensile strength: casting defects, fatigue resistance, ductility, section thickness and joining requirements may govern the choice. Compare the specified product form and verified test results rather than generic online property tables.

Heat treatment and service conditions

Solution treatment, quenching and ageing can change strength and ductility. T6 and T7 denote different treatment approaches, but actual schedules and achievable properties depend on the foundry specification. For pressure-containing or safety-critical components, evaluate porosity, leak-tightness, corrosion environment, thermal cycling and any weld-repair restrictions. A supplier’s certificate should identify the delivered condition, not merely state A356.

Practical procurement and inspection checklist

1. Confirm the applicable casting specification, alloy designation, temper and drawing revision.
2. Define critical dimensions, machining allowances and surface-finish requirements.
3. Request heat/lot traceability, chemical analysis and mechanical test evidence where specified.
4. Define radiographic or other inspection criteria for critical castings, including permitted defect levels.
5. Agree the acceptance procedure for casting repairs and reinspection before production.

Example: pump housing selection

For a pump housing, A356 may allow a complex geometry with fewer assembled parts. The engineer must still evaluate pressure integrity, mounting loads, corrosion compatibility with the fluid, temperature range and access for inspection. A casting with acceptable static strength can still be unsuitable if porosity compromises sealing or fatigue life.

Standards and further reading

Check the current editions of ASTM International specifications applicable to the particular casting product and The Aluminum Association alloy and temper resources. These are reference starting points; the purchase specification and supplier qualification documents control acceptance.

Editorial note: This is an engineering selection guide, not a certified material datasheet. Published typical properties should never replace the applicable standard, approved drawing or tested supplier certificate.