AZ31镁合金板材准静态-动态冲击流体介质温热复合成形极限研究

Research on warm compound forming limit of AZ31 magnesium alloysheet with quasi-static-dynamic impact fluid medium

基于Nakazima半球凸模胀形试验,对AZ31镁合金板材进行了成形极限试验,探究了AZ31镁合金板材在准静态-动态冲击流体温热复合成形下成形极限分布规律。结果表明,温度升高会提升AZ31镁合金板材的极限应变,对比准静态与复合成形两种方式下的极限应变发现, AZ31镁合金板材在准静态-动态复合成形下极限应变值更高,塑性成形性能得到改善。对两种成形方式下的断口形貌扫描进行分析,结果表明,准静态-动态复合成形的韧窝比准静态成形的韧窝多且深。对不同成形方式试样在室温、 100及200℃下进行了EBSD分析,发现在室温时,复合成形出现了少量{10-12}拉伸孪晶协调变形。在100℃时,复合成形引入细而薄的拉伸孪晶片层,切割细化晶粒,塑性较准静态成形得到提升。200℃下比准静态成形产生更多的再结晶晶粒是复合成形塑性提高的主要原因。

On the basis of Nakazima hemispherical punch bulging test,the forming limit tests of AZ31 magnesium alloy sheet were conducted,and the forming limit distribution rules of AZ31 magnesium alloy sheet after warm compound forming with quasi-static-dynamic impact fluid medium was studied.The results show that the increase of temperature can increase the ultimate strain of AZ31 magnesium alloy sheet.Compared the ultimate strains under quasi-static and compound forming,it is found that the plastic forming performance of AZ31 magnesium alloy sheet is improved under quasi-static-dynamic compound forming.The results of scanning analysis on the fracture morphology under two different forming methods show that the quasi-static-dynamic compound forming has more and deeper dimples than the quasi-static forming.EBSD analysis was performed on samples with different forming methods at room temperature,100 and 200℃,and it is found that a small amount of{10-12}tensile twins appear during compound forming at room temperature,resulting in coordinated deformation.At 100℃,compound forming introduces fine and thin tensile twin layers,cutting and refining grains,and improving plasticity compared with quasi-static forming.The generation of more recrystallized grains at 200℃than quasi-static forming is the main reason for its better plasticity.