size of alloy grains or size of the product made of that alloy?

in neither cases, thermodynamically speaking, solution heat treatment temperature doesn't matter. But kinetics bring time here- having a homogenization temperature higher makes solution treatment faster, and equalized chemical gradient across larger distance with ease. Al alloys are precipitation-hardened, so you probably need whole of pre-existing precipitates to dissolve, not like dissolving a certain fraction of carbides and then quenching like steel (and quenching deprends on geometry, so prerequisite of quenching also affected by it). So in short, If you are happy with prolonged time for solution heat-treating of large pices, keep your temperature as-it-is

Well

I believe that the time of the treatment is the key.

Thank you Sumit Bhowmic and Zhonyang Lu for your answers. It will definitely help me in my further research.

Temperature and soaking time matters if the size ( product dimensions, especially the thickness) is too big.

A.V.Sethuraman

Foundry Consultant

Size does matter and is problematic ! Basically activation energy is related to effect by Hollman-Jaffee: Effect= T(B+log (time)) T = absolute temp, time unit must be consistent and constant B made for best fit for ranges of times/temperature plotted to effect (hardness, UTS, % carbides etc.)

Some things we pay attentions to.... the tanks should be free of corrosion, the water should be maintained at same hardness (we prefer slightly harder water), the water temperatures should be the reasonable close regardless of climate changes and temps should not be cold.

The size of the alloy does matter to decide the solution heat treatment temperature. The solution heat treatment temperature is determined by the size of the alloy and the desired properties. The solution heat treatment temperature is usually higher for larger alloys.