Creating the Structure and Properties of 7075 Alloy Casts by Thermal and Forming Processes

Abstract

In this paper hot formability of 7075 aluminum alloy sand and permanent casting ingots has been verified. The experiment was carried out by using casting, heat treatment (homogenization) of ingots and conducting isothermal compression tests at temperatures of 420-500°C. The effect of the forming temperature on the microstructure, the tendency to crack formation and hardness has been determined. The results show that ingots in the as-cast state have a dendritic network structure rich in the second phase precipitation on the grain boundaries. After the homogenization process, the microstructure is significantly more balanced. The forming process at 420-480°C of sand casts leads to significant grain elongation and crack formation, mainly at the grain boundaries. Raising the forming temperature to 480-500°C leads to a reduction in the occurrence of cracks. On the other hand, permanent mold castings do not reveal cracks during deformation in the temperature range 420-480°C.

Keywords

• microstructure
• heat treatment
• aluminum alloys
• metal forming