Effect of unequal channel angular pressing on microstructure and mechanical properties of as cast Mg–5·8Zn–1·2Y–0·7Zr alloy

The microstructure and mechanical properties of Mg–5·8Zn–1·2Y–0·7Zr alloys before and after unequal channel angular pressing (UCAP) have been investigated in detail using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction, differential scanning calorimetry and mechanical property testing. The SEM and optical microscopy showed that the grain size was refined more at lower UCAP temperatures. When squeezed below 300°C, the average grain size was refined from the initial 110 μm to below 1·5 μm; the tensile strength increased to 390 MPa, and the elongation to break was over 13%. The high mechanical properties could be attributed to the reduced grain size and the strengthening effects of broken secondary phase particles and fine precipitates formed as a result of the severe shear and plastic deformation during pressing at high temperature.