Micro-scale model based study of solidification cracking formation mechanism in Al fiber laser welds
Micro-scale model based study of solidification cracking formation mechanism in Al fiber laser welds
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DOI：
10.1016/j.jmatprotec.2015.12.006
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发表时间：
2016-05
影响因子：
6.3
通讯作者：
XiaojieĀ Wang;F. Lu;Hui-Ping Wang;Z. Qu;Liqian Xia
中科院分区：
文献类型：
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作者：
XiaojieĀ Wang;F. Lu;Hui-Ping Wang;Z. Qu;Liqian Xia
综合考虑力学和冶金因素，研究了焊接速度对6013铝合金光纤激光焊接凝固裂纹敏感性的影响。在柱状晶粒尺度上开发了有限元模型来计算糊状区域的应变局部化。基于Rappaz-Drezet-Gremaud（RDG）准则和对所开发的微观模型的研究，以枝晶间液膜中的压降作为裂纹指标来研究凝固裂纹的形成。研究了不同焊接速度引起的冷却速率、固相率、局部应变速率和显微组织特征。 6013 铝合金光纤激光焊接中，裂纹敏感性随着焊接速度在 2.5 m/min 至 3.5 m/min 范围内的增加而降低。数值计算表明，固体颗粒中的机械拉伸应变为10−4数量级，而液膜中的机械拉伸应变为10−2数量级。柱状晶根部的总压降超过150 kPa，本研究将其视为形成裂纹的临界压降。横向凝固裂纹容易在糊状区的后半部分开始，此时固相率在90%~94%之间。
Effect of welding speed on solidification cracking susceptibility in fiber laser welding of 6013 aluminum alloy was investigated by considering both mechanical and metallurgical factors. A finite element model was developed at columnar grain scale to calculate the strain localization in the mushy zone. Based on the Rappaz-Drezet-Gremaud (RDG) criterion and study from the developed micro-scale model, the pressure drop in the inter-dendritic liquid film was used as cracking index to investigate the formation of solidification cracking. Cooling rate, solid fraction, local strain rate and microstructure characteristic resulted from different welding speeds were examined. Cracking sensitivity was shown to decrease with the increase of welding speed in the range between 2.5 m/min and 3.5 m/min in fiber laser welding of 6013 aluminum alloy. Numerical calculations showed that mechanical tensile strain in the solid grain was in the order of magnitude of 10−4while the strain in the liquid film is in the order of magnitude of 10−2. The total pressure drop at the root of columnar grains was more than 150 kPa, which was deemed as the critical pressure drop to form a crack in this study. The transverse solidification cracking was prone to initiate in the second half of mushy zone where the solid fraction was between 90% and 94%.