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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。
Through numerical simulation and microstructure observation, the cause of annular crack at the bottom of magnesium alloy cylindrical extrusion was studied. At the same time, by optimizing the forming process parameters, the crack was prevented. The results show that the main cause of cracks is that the orientation of the anti-extrusion metal flow line and the existing metal flow line are relatively large, and the adjacent crystal grains can not coordinate the anti-extrusion deformation, resulting in the local stress concentration caused by the dislocation plugging and the stress-concentration crack Nuclear and grow up. Increase the reserve base thickness and the bottom will be placed at the bottom of the cylinder, which can effectively prevent cracks.