Microstructural evolution and mechanical properties of Mg95.5Y3Zn1.5 alloy processed by extrusion and ECAP

A Mg95.5Y3Zn1.5 alloy processed via a two-step processing route of extrusion plus ECAP has been investigated. It was found that the ECAP processed Mg95.5Y3Zn1.5 alloy contained ultrafine grains and exhibited excellent mechanical properties. After ECAP, the average grain size of Mg95.5Y3Zn1.5 alloy was refined to about 300 nm. The highest strengths, with yield strength of 444.6 MPa and ultimate tensile strength of 472.7 MPa, were obtained after 1 pass at 623 K. The SAED patterns indicated that the microstructure after ECAP consisted of both high angle and low angle grain boundaries. The fraction of high-angle boundaries increased with increasing numbers of ECAP passes. The Mg95.5Y3Zn1.5 alloy contained a high volume fraction of X-Mg12ZnY phase due to high yttrium and zinc addition. And, it accelerated the growth and coalescence of cracks during tensile testing, resulting in premature fracture and lower elongation of alloy.