基于CAFE模拟钛合金丝材电弧增材制造凝固过程的组织演变

Evolution of wire+arc additive manufactured titanium alloy during solidification process based on CAFE simulation

采用CAFE(Cellular automation finite element)对Ti6Al4V合金丝材电弧增材制造的快速凝固过程进行模拟计算。通过建立不同阶段(堆积层)的三维模型,建立晶体形核与生长模型,并结合三维热传导(包含结晶潜热释放)模型,研究了不同阶段的温度场对固-液转变、初始β晶形核及生长等影响。结果表明:初始阶段初始β晶取向杂乱且晶粒尺寸细小;随着增材高度的增加,水平方向温度梯度变缓,平均固-液转变糊状区域宽度增加,初始β晶平均晶粒尺寸增加,晶体取向趋于热流传递方向(垂直于冷基板方向);其模拟结果与实际增材制造后的初始β晶组织形貌基本一致。

CAFE model was adopted to simulate the rapid solidification process of wire+arc additive manufactured Ti6Al4V alloy.Moreover,the influences of temperature field on solid-liquid transition as well as the initial I-Ti nucleation and growth in different manufacturing stages were analyzed by three-dimensional mode in different stages(deposition layer),grain nucleation and growth model and three-dimensional heat transferring(including latent heat release)model.The results show thatβ-Ti crystal has extremely disordered orientation and fine grain size in initial solidification stage(the first layer).Besides,with the increase of manufacturing sample height and the decrease of temperature gradient,both the average mushy zone width and average primaryβ-Ti grain size increase,and the crystal orientation tends to heat transfer direction(vertical cold-board direction).Final,the results of initialβ-Ti crystal growth simulation basically conform to the actual additive manufacturing.