Abstract
Microstructural evolution and flow behaviour during hot compression of twin roll cast ZK60 magnesium alloy were characterised by employing deformation temperatures of 300, 350 and 400°C and strain rate ranging from 10−3 to 100 s−1. When compressed at 10−3 s−1, all stress–strain curves at different temperatures (300, 350 and 400°C) showed a flow softening behaviour due to active dynamic recrystallisation. When compressed at 10−2 s−1 and elevated temperatures (300, 350 and 400°C), all stress–strain curves showed a flow stress drop after peak stress due to twinning for 300 and 350°C deformation and recrystallisation for 400°C deformation. The balance between shear deformation and recrystallisation resulted in a steady flow behaviour after the true strain reached 0·22. When strain rate increased to 10−1 s−1, a small fraction of dynamic recrystallisation in shear deformation region was responsible for slight flow softening behaviour during compression. A flow hardening appeared due to basal and non-basal slips when deformed at 100 s−1. It is suggested that the flow behaviour during hot compression of twin roll cast ZK60 alloy depends on the separating effect or combined effects of shear deformation, twinning and recrystallisation.