Influences Of Element Sb And Hot Extrusion Treatment On Microstructure And Mechanical Properties Of AZ31 Alloys

In the paper, the influences of the element Sb and hot extrusion treatment on microstructure and mechanical properties of AZ31 alloy with T6 and extruded states are investigated by means of OM SEM TEM observation and measurement of mechanical properties.Results show that the microstructure of AZ31 alloys which is alloyed with the element Sb consists ofα-Mg matrix, Mg₁₇Al₁₂ and Mg₃Sb₂2 phases which have high melting point and are dispersedly precipitated in the matrix, which may obviously improve the properties of alloys. The mechanical properties of AZ31 alloys at RT and high temperature can be enhanced with the increasing of the element Sb. The ultimate tensile strength (UTS) of AZ31 alloy with T6 treatment at RT is enhanced to 297MPa from 222MPa as the content of element Sb is increased to 0.84(wt)%. Compared with AZ31 alloy, the extent of the increased UTS is up to 33.8%.The mechanical properties of AZ31 and AZ31-0.25%Sb alloys at RT and high temperature can be effectively improved by means of hot extruding treatment, and the UTS and YTS of the alloy increase with the decrease of extruding temperature. After extruded at 360℃, the UTS of AZ31 alloy at RT is increased to 276.9MPa from 222MPa, and YTS of the one is increased to 210.7MPa from 84MPa, the extent of the increased UTS is up to 150.8%. By means of extruded at 220℃ageing treatment at 180℃, the UTS of AZ31-0.25% Sb alloy at RT increases to 297.6 MPa from 263MPa, and the YTS of the one at RT increases to 222.1 MPa from 96MPa, so that the extent of the increased UTS is up to 131.4%.The main reasons that the mechanical properties of the alloys are improved by extruding treatment are attributed to the deformation strengthening and dynamic recrystallization occurred during extruded treatment. The fact that the denser dislocations come from during deformation may result in the effect of deformation strengthening, and some of the finer particle precipitated during ageing display an obvious effect of second phase strengthening. In the further, the fact that the dynamic recrystallization occurs during hot extrusion possesses an obvious effect of decreasing grains size, which may effectively enhance the YTS of the alloys.The deformation features of AZ31-Sb alloys during tensile deformation at RT and high temperature are that the twinning deformation and dislocation slipping in the twins. Thereinto, the main mechanisms of deformation are a dislocation slipping on the basal plane and a + c dislocation slipping on pyramidal planes. The main features of tensile deformation at 150℃are a dislocation slipping on the basal plane and a + c dislocation slipping on prism planes and half pyramidal planes.