Effect Of Differential Speed Rolling On Microstructure Of AZ31 Magnesium Alloy Sheet

The wrought magnesium alloy sheets exhibit great potential for applications due to their excellent mechanical properties. While the well developed basal texture during the traditional equal speed rolling(ESR) limits the plasticity and the secondary formability. The additional shear strains exist in the differential speed rolling(DSR) modify the basal texture, which can enhancing the secondary formability and reducing the cost of rolled magnesium alloy sheets.In this article, analysis techniques like optical microscope(OM), micro-hardness test, tensile machine, scanning electron microscope(EBSD), X-ray diffraction(XRD) were used to analyze mechanical properties and microstructure of DSRed AZ31 sheets.The results show that the samples processed by differential speed pre-rolling shows more fine and uniform microstructure than that of the ESR-processed sample. Also, the differential speed pre-rolling can promote the modification of texture and the rotation of the basal planes toward to ±TD. The weaken and inclined basal texture probably results from the higher fraction of DRX grains that the misorientation angle is around 30 o in the differential speed pre-rolled sample especially at speed ratio SR of 1.5. Also a wide peak around 86 o which stems from {1 0 2} extension twinning boundaries is also noted in the sample of differential speed pre-rolled at SR of 1.5, which can modify the texture.The samples processed by differential speed pre-rolling at SR of 1, 1.2, 1.5 and 1.7 are damaged at the reduction of 21%, 24%, 26% and 24%, respectively. This means the sample processed by pre-rolling at SR of 1.5 shows better rolling capacity than others.The rolling route rotating rolling and normal directions simultaneously, can homogenize grain size, weaken basal texture. This route shows intersectional shear bands and uniform microhardness, higher ductility and strength.In the SR range of 1-1.5, the increase of the SR is beneficial to reduce the basal texture and improve the formability sheet of magnesium alloys sheet. When the SR is 1.5, the increase of the rolling temperature can reduce the basal texture of magnesium alloys sheet. When the SR is 1.5, the texture of 10% rolling reduction was lower than 5%, which can reduce the cost of industrial production. In conclusion, the best DSR technical parameters are that the SR is 1.5, rolling temperature is 400 °C, rolling reduction is 40% and rolling reduction per pass is 10%.