Abstract

Porosity is one of the significant defects existing in the weld seam of aluminum alloy by laser. In the current research, the evolution of porosity and grain coupling growth in the weld seam is realized via a Cellular Automaton-Finite Element simulation method. A detailed calculating method of three phases was proposed by taking into account the liquid/solid phase transformation on the nucleation and growth of porosity. The results show that the porosity nuclei with larger size can grow preferentially, while the small porosity nuclei's development is inhibited. Because of the effect of gas/liquid surface tension, porosity increases spherically when it is enveloped by liquid. After touching with grain, the porosity's growth space is restricted by the complex dendrite network, and thus its shape becomes irregular. The coupling of grain and micro-porosities predicted by the simulation method is in good agreement with the results obtained by the experiments.

摘要

气孔是激光加工铝合金焊缝中存在的重要缺陷之一。在目前的研究中，焊缝中孔隙度和晶粒耦合增长的演变是通过元胞自动机-有限元模拟方法。考虑到液相/固相转变对孔隙成核和增长的影响，提出了三相的详细计算方法。结果表明，尺寸较大的孔隙核优先生长，而小孔隙核的发育受到抑制。由于气/液表面张力的影响，当它被液体包围时，孔隙率呈球形增加。与晶粒接触后，孔隙的生长空间受到复杂的枝晶网络的限制，因此其形状变得不规则。模拟方法预测的晶粒和微孔的耦合与实验得到的结果非常吻合。