Numerical and experimental study on the extrusion through a porthole die to produce a hollow magnesium profile with longitudinal weld seams
Numerical and experimental study on the extrusion through a porthole die to produce a hollow magnesium profile with longitudinal weld seams
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DOI：
10.1016/j.matdes.2007.05.003
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发表时间：
2008-01-01
影响因子：
8.4
通讯作者：
Zhong, Z. H.
中科院分区：
文献类型：
--
作者：
Li, L.;Zhang, H.;Zhong, Z. H.
本研究揭示了AZ31B镁合金在通过舷窗模具挤压成形方管过程中的热力学行为。三维数值模拟结果表明，在挤压循环的初始阶段，金属流进挤压孔、焊接腔和模具轴承的过程与挤压压力的阶梯式增大相对应。挤出压力和挤出温度的实验测量结果与预测值基本一致。挤压压力在压力峰值后持续下降，而工件温度稳步升高，导致挤压物的再结晶晶粒尺寸沿其长度逐渐增大。挤压过程中，焊接平面温度升高，焊接室最大法向压力降低，但纵向焊缝质量沿挤压长度方向一致。因此，决定焊缝质量的是焊接腔内的最大正常压力与焊接平面上工件材料的流动应力之比。(C) 2007 Elsevier Ltd.版权所有。
In this study, the thermomechanical behaviour of a magnesium alloy AZ31B during extrusion through a porthole die to form a square tube was revealed. Three-dimensional numerical simulation demonstrated that metal flow into the portholes, welding chamber and die bearing of the porthole die corresponded to the stepped increases of extrusion pressure at the initial stages of an extrusion cycle. Experimental measurements of extrusion pressure and extrudate temperature were found to be in agreement with the predicted values. Extrusion pressure decreased continuously after the pressure peak while the workpiece temperature increased steadily, leading to gradual increases of the recrystallised grain sizes of the extrudate along its length. Expansion tests showed consistent quality of the longitudinal weld seams along the extrudate length, although the temperature on the welding plane increased and the maximum normal pressure in the welding chamber decreased during extrusion. It is thus the ratio of the maximum normal pressure in the welding chamber to the flow stress of the workpiece material on the welding plane that determines the weld seam quality. (C) 2007 Elsevier Ltd. All rights reserved.