Effect of hot rolling on the microstructure and mechanical properties of Mg–5Al–0.3Mn–2Nd alloy

Abstract

Mg–5Al–0.3Mn–2Nd alloy was prepared by metal mould casting. The as-cast ingot was homogenized, and then hot-rolled with total thickness reduction of 63%. Further annealing treatment was carried out on the hot-rolled sample. Microstructure and mechanical properties of the studied alloy in as-cast, hot-rolled and annealed states were investigated. Results showed that main phases of the as-cast sample were composed of α-Mg, Al 2Nd, Mg 17Al 12 and Al 11Nd 3. While for the hot-rolled and annealed samples, no Mg 17Al 12 phase was detected. Average grain size of the as-cast sample was about 90 μm. After hot rolling, average grain size was greatly refined to about 20 μm. Furthermore, the long acicular Al 11Nd 3 phase broke into many small sections. Tensile test results showed that ultimate tensile strength and yield strength of the hot-rolled sample were 340 MPa and 240 MPa, respectively. Compared with those of the as-cast sample, they were enhanced by 47.8% and 269% correspondingly. However, elongation greatly decreased to 9%. Through annealing treatment, elongation recovered to more than 24% again.