定向凝固包晶相变微观组织演化的相场方法研究Ⅱ.形核控制的微观组织模拟

采用包晶相变相场模型分别模拟了高G／vp定向凝固Ti—Al合金在小直径试样的连续形核和大直径试样的多重形核情况下，包晶两相微观组织演化．模拟结果表明，对于小直径试样，减小试样尺寸或减小包晶相形核过冷度倾向于形成岛屿带状组织；而对于大直径试样，包晶相所占体积分数以及形核率的不同将导致形成离散带状、岛屿带状和耦合生长组织．

PHASE-FIELD RESEARCH OF MICROSTRUCTURE EVOLUTION FOR DIRECTIONALLY SOLIDIFIED PERITECTIC TRANSITION II.Simulation of Nucleation-Controlled Microstructure

The microstructure evolution of both phases is simulated by the phase-field model of peritectic transition for directionally solidified Ti-Al alloy at a high value of Give when the continuous nucleation occured to a sample with a small diameter and the multiple nucleation occured to a sample with a big diameter. The simulated results show that for the small sample decreasing sample size or nucleation undercooling of peritectic phase tended to form island band structure. But to the big sample, the differences of the volume fraction of peritectic phase and the nucleation rate cause to form the discrete band, island band and coupled-growth structures.