Experimental investigation of limit drawing ratio for AZ31B magnesium alloy sheet in warm stamping

As a promising solution to lighter vehicles, warm stamping of magnesium alloy sheet has gained intense attention in automotive industry. Firstly, boron nitride (BN), graphitic (C), molybdenum disulfide (MoS2), and polytetrafluoroethylene (PTFE) were evaluated as high-temperature lubricants for magnesium sheet forming. BN demonstrated the best comprehensive performances for good lubrication effect, load-carrying capacity, and excellent low-cost water washing convenience. Limit drawing ratio (LDR) was then determined for 1.5-mm-thick AZ31B magnesium sheet with and without BN as lubricant, and LDRs of 2.5 and 2.1 were achieved for lubricated and unlubricated situations. It was demonstrated that lubricated LDR of AZ31B magnesium sheet under warm stamping is comparable to most known mild steel sheets. The discussion through lubrication status and sheet thinning investigated the effect of lubricant on the increase of LDR compared with unlubricated case.