Study On The Microstructures And Properties Of Mg-3Zn-0.2Ca-0.5Y Mg Alloy Sheet Produced By Rolling

As the lightest metallic structure material, magnesium(Mg) and its alloy has been more and more widely used in the areas of national defense and civil products. Thus, many researchers focus on optimizing the processing technology to obtain the high performance and low anisotropy Mg alloys sheet.In this paper, choosing the as-extruded micro RE-alloying Mg-Zn-Ca-Y bar as the initial billet and investigating the microstructure, texture evolution and the effect of Ycontaining second phase during the rolling process in order to explore a rolling process for fabricating high-performance Mg alloys sheet. At the same time, the influence of the different rolling temperature, reduction and the different rolling method on the microstructure and mechanical properties were analyzed. The effect of different rolling ways on the room-temperature formability of RE-containing Mg alloy was investigated by comparing the r-values of the sheets by unidirectional rolling and cross rolling.Putting forward ―the rod to sheet‖ rolling process to roll the initial billet. In this way, the special texture of extured rod was fully considered and the basal slip, deformation twinning and non-basal slips systems were activated during rolling process. The weakened texture and more random grain orientation were obtained due to multiple deformation mechanisms. The average grain size of as-rolled sheet was refined to 5.88μm by the rolling way and the yield strength achieved 180 MPa with an excellent untimate elongation of 40%. In addition, the little difference of mechanical properties between RD and TD and the lower anisotropy are obtained in the sheets after rolled by this way, indicating that provides a vast space for the application of magnesium alloy sheet.Meanwhile, by comparing the effects of different rolling reduction, temperatures and rolling method on the microstructure and mechanical properties of Mg alloys, it is found that the rolling temperature mainly affects the second phase precipitation. Moreover, the tiny and dispersed second phase particles were obtained at relatively lower rolling temperature and they improved the strength of as-rolling sheet obviously. The weaker texture intensity, the finer grain size and the higher recrystallization dynamic recrystallization degree can be achieved by increasing the rolling reduction. Compared with unidirectional rolling, the sheet rolled by cross rolling exhibited the weaker texture intensity, lower anisotropy, higher r-value and better formability. All of the above-mentioned indicates that it has greatly importance to enhance the secondary formability of Mg alloys sheet. Analysizing the three factors which influence the formability comprehensively, a conclusion can be achieved that the hot cross rolling with larger reduction is a very effective route for fabricating a high performance Mg alloy sheet.