Aging Yes, Solution Treatment Mostly No
The trapped-gas problem
Conventional high-pressure die castings contain entrapped air and gas from the shot process. Solution treatment pushes metal above the solidus range, and the trapped gas expands into surface blisters. This is why classic T6 schedules are off the table for most HPDC parts.
Vacuum-assisted casting and squeeze casting reduce trapped gas enough to make solution treatment feasible for some applications, at higher process cost.
T5 aging: the practical path
Aging below the solidus raises strength in heat-treatable alloys without melting the trapped gas phase into blisters. The gain is smaller than full T6, but for housings and brackets it is often enough and it costs little.
Aging also relaxes residual stress, which helps parts that will be machined afterwards: less movement after the metal is cut away.
Dimensional stability treatments
Parts requiring tight tolerances over service life, such as machined hydraulic components, often get a dedicated stabilization cycle. Time and temperature are chosen to relax stress while staying safely below the blistering threshold.
Any heat treatment must be qualified with blister inspection and dimensional checks on real parts, because alloy chemistry, casting density and section thickness all move the safe window.
FAQ
Why do die castings blister during solution treatment?
High-pressure die castings trap gas in the metal. Solution temperatures exceed the solidus range and the trapped gas expands, raising surface blisters. Vacuum or squeeze casting reduces gas enough to permit it in special cases.
What is T5 versus T6 for die castings?
T5 ages the as-cast part below the solidus to raise strength; T6 adds full solution treatment. Conventional die castings use T5 because T6 blisters gas-containing parts.
Does aging help dimensional stability?
Yes. Aging and stress-relief cycles relax residual casting stress, so machined surfaces and tight features move less after machining.
Can heat treatment fix porosity?
No. Heat treatment changes strength and stress state; it cannot fill voids. Porosity is controlled upstream through process parameters, vacuum assistance and die design.
All figures above refer to standard product data sheets; final confirmation is subject to written quotation.