Abstract
The Al-12.2% Si and Al-12.2% Si-0.8% Mg alloys were prepared with metallic molds. The changes of their properties such as hardness, mean free path between silicon particles, and mean radius of silicon particles were studied after annealed at 400-500°C to determine the working conditions of the alloys. Some mechanical properties of these sheets were examined after hot-rolled and finally cold-rolled to 0.5mm in thickness.
The main results obtained were as follows:
(1) The hot and cold working of these alloys were made possible by the increase of mean free path and mean radius of silicon particles, due to an appropriate annealing at about 500°C for 3hr. The intermediate annealing at about 300-350°C for 1hr. was required during the process of cold-rolling of thes alloys.
(2) The mechanical properties of the above rolled sheets were superior to those of any other practical alloys of the same type. For example, tensile strength, elongation, and hardness of cold-rolled Al-l2.2% Si sheet were 24kg/mm2, 3%, and Hv 66, respectively. Those of Al-12.2% Si-0.8% Mg sheet were 25kg/mm2, 14%, and Hv 55 in solution heat-treated state, respectively; and 37kg/mm2, 8%, and Hv 107 in T6 treated state, respectively.
(3) Microstructure of the both rolled alloys showed the almost uniform dispersion of silicon particles, but no rupture of particles during working.
