Effect of LPSO Phase Control on Microstructure and Mechanical Property of ECAP Processed Mg-Y-Zn-Al Alloy
Aiming at the problems of poor plasticity and toughness of as-cast Mg-Y-Zn alloys containing 18R-LPSO phase and limited improvement of mechanical properties after deformation,the effects of solid solution,as-cast+ECAP extrusion and solid solution+ECAP on mechanical properties of Mg-3.74Y-1Zn-0.5Al(at%)alloy were studied.The results show that the solution treatment induces 18R→14H-LPSO phase transformation and the Al(Y,Zn)phase compound particles are broken and refined,which improves the plasticity of the alloy,but the strength is almost unchanged.Cast+ECAP extrusion leads to the fragmentation of 18R-LPSO and Al(Y,Zn)phases,and induces recrystallization of a large number of α-Mg grains.Solid solution+ECAP extrusion makes 14H-LPSO bend or kink,fine Al(Y,Zn)particles are uniformly dispersed,and only a few of α-Mg grains recrystallize,and its strength,ductility and toughness are much higher than those of cast+ECAP alloy.The main reasons for the improved performance are the large formation of 14H-LPSO phase with good strength-plasticity-toughness matching,the suppressed recrystallization of α-Mg matrix and the uniform dispersion of fine Al(Y,Zn)particles.
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