Effects of Degassing Conditions in Fabrication Process on Mechanical Properties of High Strength P/M Aluminum Alloy Sheets Made from Alloy Powder

Abstract

The rolled sheets were made by P/M method from 7091 alloy powder, and effects of degassing conditions on mechanical properties and microstructures were studied. The green compacts of the powder were encapsulated, and degassed at 653 K-773 K for 0.3 h-24 h in about 10^-3 Pa vacuum. Following degassing, the compacts were hot pressed, hot rolled with 88% reduction, and then cold rolled with 67% reduction to obtain 1 mm thick sheets. Results obtained were as follows:
1) The degassing conditions considerably influenced the ultimate tensile strength (UTS) and the yield strength (YS) of the P/M sheets in T6 temper. The P/M sheets made through degassing at 733773 K for I h or more showed the highest UTS of about 630 PMa.
2) The recrystallized grain size of the P/M sheets in T6 temper was also influenced by the degassing conditions, and the relatively high degassing temperatures of 733-773 K led to fine grain size.
3) The P/M 7091 alloy sheets made through degassing at 733 k for 1 h showed higher UTS than those of I/M 7091 and I/M 7075 alloy sheets in T6 temper, and the differences were 35 MPa or more.