Press Formability Properties And Drawing Technology Of AZ31 Magnesium Alloy Sheet

The drawability and technique of AZ31 magnesium alloy sheet processed by two different rolling processes are investigated. The results show that compared with as-received sheet, grains are finer and basal texture,yield strength,yield ratio,plastic strain ratio all decrease, while strain hardening exponent increases for AZ31 magnesium alloy sheet processed by equal channel angular rolling(ECAR) at room temperature. This means the drawability of AZ31 magnesium alloy sheet can be improved effectively by ECAR process. With deformation temperature increases, the formability of both sheets increase obviously, and these sheets have the equivalent formability at the range of 200~300℃. At room temperature, the limiting drawing ratio(LDR) of the as-received sheet is only 1.2, while which of as-ECARed sheet achieves 1.6, which has better drawability. Compared with the as-received sheet, the value of Erichsen for as-RCARed sheet is obviously much higher, which has better bulging formability.The warm drawing process of both sheets are also investigated, the results indicate that LDR of 1.76 can be achieved at 160℃for the sheet processed by ECAR; but for as-received sheet, only when the temperature is higher than 180℃, drawing can be proceeded. At 220℃,when Rp=8mm,Rd=10mm,C=1.12t,drawing velocity is 12 mm/ s and lubricating by graphite and oil, the cup workpiece of AZ31 magnesium alloy with good surface quality and LDR of 2.53 can be obtained. Further investigating indicates that formability of magnesium alloy is obviously improved with temperature increases, but the drawability of AZ31 magnesium alloy sheet processed by ECAR hasn't visible advantage compared with as-received sheet. The microstructure of flat-bottom stamping cup indicates that twins occur more or less at some place which is perpendicular and parallel to the ECAR direction, and in the perpendicular direction there are relatively more twins. So the formability is stronger at fracture which is perpendicular to the ECAR direction, therefore it doesn't tend to crack.