Recently, being producing the various products of Al alloys by impact extrusion, they studied on the high temperature impulsive hardness of Al and its alloys by means of Honda and Sato's impulsive hardness tester.
They arrived at the following conclusions:
(1) At room temperature, the volume of indent in all alloys is proportion to the deformation energy with exception of a small amount of deformation.
(2) Impulsive hardness is almost proportion to Brinell Hardness Number (500kg/10mmφ).
(3) High temperature impulsive hardness of Al is gradually decreased by heating.
But, there is a hardening temperature range (200-300°C) in the case of binary and high strength Al alloys. These hardening are due to the solubility of additional elements and their intermetallic compounds to Al.
(4) These hardness changes were discussed by observing the macrostructures.