Study On The Microstructures And Mechanical Properties Of Reciprocating Extrusion Mg Alloys

Mg alloys possesses low density, high specific strength, good damping capacity and other favorable properties. However, their comprehensive applications limited by low absolute strength. In this paper, the effects of reciprocating extrusion (RE) and heat treatments on Mg-Zn-Y and Mg-Zn-Si alloys were studied to broaden the applications of Mg alloys. The compositions of Mg-Zn-Y alloys are Mg94.6Zn4.8Y0.6, Mg92.5Zn6.4Y1.1, Mg91.6Zn7.2Y1.2 (at%); The composition of Mg-Zn-Si alloy is Mg-6Zn-5Si (wt%). Rapidly solidified (RS) Mg-Zn-Y and as-cast Mg-Zn-Si alloys were reciprocally extruded by different passes and then heat treated. The microstructures and phase compositions of the alloys were studied by optical microscope, transmission electronic microscope, X-ray diffraction and differential thermal analysis. The mechanical properties of the alloys were measured by hardness and tensile testings, and the thermal expansibilities of RE as-cast Mg-Zn-Si alloys were also tested by thermal mechanical analysis. The conclusions are as follows:1. RS Mg-Zn-Y alloys ribbons can be processed by RE to obtain bulk materials successfully. RE by more passes could promote the precipitation of dispersed I phase.2. The ultimate tensile strength of RE RS Mg-Zn-Y alloys increase with the Zn and Y. aging treatment improves the yield strength of RE RS Mg-Zn-Y alloys greatly.3. RE can refine the micristructures of as-cast Mg-Zn-Si alloy and improve its uniformity greatly, especially to the hard and coarse Mg2Si particles.4. After being water quenched and aged, the yield strength and ultimate tensile strength of Mg-Zn-Si alloy increase obviously.5. RE can improve the stability of thermal expansibility of as-cast Mg-Zn-Si alloy.