Effects of Different Mass Ratio Copper, Zinc on Microstructure and Properties of Mg-Zn-Cu Alloys

Abstract:

The effects of cerium and different mass ratio Cu:Zn on the microstructures and mechanical properties of Mg-Zn-Cu alloys were investigated. The optical microscope, X-ray diffractometer, scanning electron microscope were introduced in the experiments. The microhardening testing, room and high temperature tensile test and creep properties test were done to study the effect of Cu content on the properties of the alloys, such as the evolution rule of its room and high temperature mechanical property, hot deformation behavior, strengthening mechanism and resistant creep behavior. The tensile strength and yield strength of extruded Mg-8Zn-8Cu-Ce are 320 MPa and 291 MPa respectively at room temperature, and its tensile strength is still higher than 220 MPa at 423 K. The alloy has best creep property; the steady creep speed rate is 1.21 × 10_-8 s_-1 with the creep strain 0.562% only. At the same deformation temperature, the true stress level of the as-cast Mg-7Zn-3Cu-Ce alloy increases with increasing of the strain rate. The result indicates that the alloy is strain rate sensitive material. While at the same strain rate, the true stress level of the alloy declined with the temperature increased. There is no obvious dynamic recrystallization and the softening effects.

Key words:magnesium alloy; microstructure; high temperature properties; creep; hot deformation