Stuy On Phase Equilibra And Cold Drawing Process Of Mg-Zn-Y-Ca Alloys

In this paper,the as-cast microstructures,the phase equilibria in the Mg-2Zn-xY-yCa(x=0.5,0.8,1.0,1.3;y=0,0.3;wt.%)magnesium alloys have been studied;and the effects of Y and Ca contents on microstructure and mechanical properties of as-extruded Mg-2Zn-xY-yCa alloys have been investigated.Based on this,the as-extruded MgZn2Y1.0Ca0.3 and MgZn2Y1.3Ca0.3 alloys were used in the cold drawing process to make F 2.6mm and F 3.0mm magnesium alloy wires.The as-cast Mg-Zn-xY-0.3Ca(x=0.5,0.8,1.0,1.3)alloys mainly consist of a-Mg matrix,W-Mg3Y2Zn3,T1-Ca2Mg6Zn3 compounds.The microstructure is gradually refined and the number of ternary compounds increases with the increasing of Y content,meanwhile the precipitation phases finally form a net on the grain boundary of α-Mg.The as-cast MgZn2Y0.8 alloys mainly consist of a-Mg matrix and W-Mg3Y2Zn3 compounds.After equilibrium treatment at 400 ℃ for 14 days,Mg-Zn-xY-0.3Ca(x=0.5,0.8,1.0,1.3)alloys mainly consist of α-Mg matrix,W-Mg3Y2Zn3 and Mg2Ca.Meanwhile,the MgZn2Y0.8 alloys mainly consist of a-Mg matrix and W-Mg3Y2Zn3 compounds.Microstructure analysis of extruded Mg-Zn-xY-0.3Ca(x=0.5,0.8,1.0,1.3)alloys shows that the average grain size decreases from 8.1 μm to 4.33μm with the Y content increasing from 0.5 to 1.3w.t%.Compared with MgZn2Y0.8,the addition of 0.3wt.%Ca leads to grain refining obviously.Mechanical propertity analysis shows that the yield strength of alloys containing Y from 0.5wt.%to 1.0wt.%increases from 149MPa to 171MPa,tensile strength increases from 233 MPa to 250MPa,and the elongation can reach to 20%.Alloys containing 1.3wt.%Y have the highest yield and tensile strength of 171MPa and 250MPa respectively,but the elongation decreases to 21.1%.Cold drawing and annealing technologies were used to MgZn2Y1.0Ca0.3 and MgZn2Y1.3Ca0.3 alloys.The deformation,annealing temperatures and annealing time were studied during recrystallization.The final annealing temperature and time were determined to be 350℃×30min and 370℃×30min,where the grain size after crystallization is between 3.5μm to 4μm,and the lagest deformation can be performed to the alloys.After multiple-pass wire drawing,MgZn2Y1.0Ca0.3 and MgZn2Y1.3Ca0.3 wires with diameters of(?)2.6mm and(?)3.0mm were made in this work.