Hot deformation of PM Al6061 alloy produced by sintering and powder extrusion

Abstract

Compression test was used to study the deformation behaviour of sintered (12% porosity) and powder extruded (1% porosity) Al6061 alloy at high temperatures ranging from 350 to 500°C. The flow curves of the materials were determined at strain rates of 0·001, 0·01 and 0·1 s⁻¹. The extruded alloy exhibited plastic instability in the form of bulging and formation of shear bands. The deformation activation energy of the extruded material was determined to be Q _I=77±16 kJ mol⁻¹ (T<450°C) and Q _II=136±12 kJ mol⁻¹ (T≥450°C). The values of activation energy and appearance of strain softening in the stress–strain curves revealed that thermally activated restoration processes, i.e. dynamic recovery and dynamic recrystallisation, occurred. The sintered compact exhibited geometrical strain hardening during deformation with a limited ductility at temperatures <450°C. Pores and cracks were formed in the bulged region due to localised tensile stresses.