Aluminum alloys get much of their final strength from a heat treatment that takes only hours but is often misunderstood. For casting alloys such as A356, the difference between 'as-cast' and 'T6' can be roughly 40% in yield strength.
T4 and T6 are the two designations buyers meet most. They are not options to tick casually — they change the whole process window and the price.
Key Points
- T4 = solution treatment + natural aging: improves ductility and impact resistance, good for parts that will be bent or formed after casting.
- T6 = solution treatment + quenching + artificial aging: maximum strength and hardness; the standard choice for structural and pressure-bearing castings.
- Quenching after solution treatment is the risky step — distortion risk means the casting should be machined after T6, not before.
- When to pay for it: safety parts, thin-wall parts under load, anything that must pass a pressure or fatigue test. Our facility runs age-effective furnaces in-house.