Microstructural and mechanical effects of Liquid Hot Isostatic Pressing on AA356 samples. i.

Abstract

Comparative tensile tests and microscopic images are reported of AA356 samples subjected to solubilization, quenching in water and T6 aging (as cast), and on samples of the same alloy subjected in addition, at the end of the solubilization period, to Liquid Hot Isostatic Pressing (LHIP). LHIPing is a recent technical variant of conventional HIP-ing, where the pressure is transferred to the metallic components through molten salts rather than through a gas.

Different solubilization times (1 ÷ 8 hours) at the temperature of 520 °C have been explored. The results confirm that, provided that the solubilization time exceeds 3 hours, LHIP-ing improves strongly the elongation to fracture and sensibly improves the ultimate tensile strength, UTS, practically without affecting yield.
In order to assess criteria for optimizing the casting process, the mechanisms of HIP-ing
and their roles in the densification and the improvement of the ductility of the alloy are qualitatively analyzed for the specific heat treatments and LHIP parameters adopted in the present study.