Ti-6Al-4V合金中片层组织形成的相场模拟

Ti-6Al-4V是典型的α+β钛合金，不同热处理制度和热加工工艺下可得到形貌各异的微观组织，从而表现出不同的力学性能，深刻理解合金中微观组织的形成机制有助于合金的进一步优化和改造.采用相场方法模拟Ti-6Al-4V合金中片层组织的形成及演化，以热力学数据库和动力学数据库为输入，通过计算定量预测β晶界上已存在初生α相时合金组织随时间的演化.结果表明，在一定条件下，随着时间的延长晶界α向β晶内生长形成片层组织，片状α簇的形貌与界面能各向异性密切相关；晶界取向对片层生长有重要作用，垂直于晶界生长时产生最密集的片层，随倾斜角增大片层加厚且生长缓慢；此外，热处理温度显著改变片层组织形貌，温度越高，片层尖端生长速度越慢，片层间距越大. 关键词： Ti-6Al-4V 相场模拟 片层组织

Phase field simulation on sideplates formation in Ti-6Al-4V alloy

Ti-6Al-4V is a typical α+β titanium alloys. It presents the diversiform microstructures and thus various properties under different heat-treatment regimes and thermomechanical conditions. The thorough understanding of the formation mechanisms and the evolution rules of different microstructures is crucial to the optimization of the alloys. In this paper, the formation and the evolution of sideplates in Ti-6Al-4V alloy are simulated by using phase field method, with the thermodynamics and the mobility databases used as the input of the phase field model and the primary α phase assumed to exist at the grain boundary. The simulation results show that under a certain condition the grain boundary α phase can grow into β matrix and form sideplates, and that the morphology of α colony is related to the interfacial energy anisotropy. The grain boundary orientation has a strong effect on the sideplate structure. In addition, the heat-treatment temperature can also change the morphological features of sideplates. Higher temperature can slow down the growth of sideplates and result in wider sideplate spacing as well.