The Study On Microstructure And Mechanical Properties Of Ultrafine-grained Mg-Y-Nd Alloy Processed By Equal Channel Angular Pressing

Mg-Y-Nd alloys have excellent corrosion resistance,good biocompatibility,thermal stability and excellent comprehensive mechanical properties.However,at room temperature,the ability of plastic forming is very poor,so the application is limited.Refine the grain size is also important way to improve the strength of magnesium alloy and plastic toughness,the fined-grained Mg-2Y-0.6Nd-0.5Zr alloy was prepared by equal channel angular pressing(ECAP)in this paper.,by optical metallographic microscope(OM),scanning electron microscope(SEM),XRD and other analysis methods,studied in the process of pressing Mg-2Y-0.6Nd-0.5Zr alloy change process of the organization.Of the samples before and after the extrusion microhardness,room temperature tensile testing of the mechanical properties and tensile fracture,analysis after 1?2?3?4?6 and 8 times after extrusion,in the process of extrusion deformation of the channel such as corner,the alloy extrusion passes the evolution of organizational structure and mechanical properties at room temperature.First of all,through the optimization and design of the channel corner extrusion die,the sample can be successfully pressed,and the uniformity and surface quality of the sample tissue are better.Secondly,the effects of different homogenization time and temperature on the microstructure and mechanical properties of Mg-2Y-0.6Nd-0.5Zr alloy were studied.After 450?×6 h after processing,microstructure of rich and rich Nd phase is largely Y most decomposition diffusion into the substrate.After the homogenization of different temperature and time,the grain size of the alloy was grown.Homogenization treatment the higher the temperature,the lower the hardness value,with the extension of heat preservation time,the hardness are the trend of decline,a relatively short period of time,the hardness decreased obviously,but with the heat preservation time after 6 h,hardness tends to slow down;Finally,the Mg-2Y-0.6Nd-0.5Zr of ECAP for alloys with different extrusion deformation,through to the ?=120° and ?=30° after ECAP Bc path of 1?2?4?6 and 8 times by equal channel angular pressing,Mg-2Y-0.6Nd-0.5Zr alloy tissue significantly by refining grain size,six times the average grain size after extrusion for about 5 ?m.With the increase of ECAP passes,the grain size gradually decreases,and the structure of the alloy structure becomes more uniform,and after the extrusion of 6 times,the homogeneity of the alloy is also the best.The microhardness and room temperature mechanical properties of Mg-2Y-0.6Nd-0.5Zr alloy were significantly improved after multi-channel angular compression.The tensile strength and microhardness of the alloy have reached the highest with the increase of the extrusion channel.After 8 times,the hardness decreased.After the multi-channel angular presses,the temperature fracture mechanism of Mg-2Y-0.6Nd-0.5Zr alloy was transformed from brittle fracture to ductile fracture.