镁合金筒形挤压件底部裂纹产生机理和防护
Generating Reason and Protection of Crack of Magnesium Alloy Extruded Cylinder at Bottom
孟 模， 张治民， 杨 光， 李新凯
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作者单位：Generating Reason and Protection of Crack of Magnesium Alloy Extruded Cylinder at Bottom
中文关键字：镁合金； 筒形挤压件； 环形裂纹； 参数优化
英文关键字：magnesium alloy; extruded cylinder; ring crack; optimization of parameters
中文摘要：通过数值模拟和微观组织观察，研究了镁合金筒形挤压件底部环形裂纹产生的原因，同时通过优化成形工艺参数，防止裂纹产生。结果表明：裂纹产生的主要原因是反挤金属流线和已有金属流线的取向较大，相邻晶粒无法协调反挤变形，导致位错塞集引起局部应力集中，应力集中处裂纹形核并长大。增加预留底厚和将预留底置于筒形件底部，可有效防止裂纹产生。
英文摘要：The reason of generating crack at the bottom of magnesium alloy extruded cylinder was studied by numerical simulation and microstructure observation. At the same time, the forming process parameters were optimized to prevent generating cracks. The results show that the crack is mainly caused by very different orientation between anti-extrusion metal flow lines and existing metal flow lines, which make neighboring grains not coordinate anti-extrusion deformation, lead to the dislocation accumulation at the die's corner，where the crack arises and expands owing to stress concentration. The crack can be effectively prevented by thickening bottom and remaining bottom at the end of extruded cylinder.