Microstructure and mechanical properties of the hot-rolled Mg-Y-Nd-Zr alloy

摘要

Microstructures and mechanical properties of the Mg-4Y-2.5Nd-0.6Zr (wt%) alloy in the as-cast, as-rolled, and rolled-T5 conditions have been investigated. Results showed that the as-cast sample mainly consisted of the α-Mg matrix, network-like Mg_(41)Nd_5 phase, and cuboid-shaped Mg_(24)Y_5 particles. For the as-rolled sample, the thermally stable Mg_(24)Y_5 particles located at both grain boundaries and matrix, and the average grain size was greatly refined to about 15 μrn. Yield strength, ultimate tensile strength, and elongation of as-rolled samples were 290 MPa, 235 MPa, and 10%, respectively. They were enhanced by 48.7%, 56.7%, and 38.9% correspondingly compared with those of the as-cast sample. After isothermal aging at 250 ℃ for 4 h, the optimal mechanical properties can be obtained. Besides, the tensile strengths of as-rolled and rolled-T5 samples decreased gradually with a gradual increase of ductility from room temperature to 300 ℃. Quasicleavage and cleavage fracture were the fracture patterns of as-rolled and rolled-T5 samples, respectively, at room temperature. For samples under the two conditions, fracture mode similarly changed with the increase of test temperatures, and ductile fracture can be observed at higher temperature.