【摘要】 利用合金凝固热力学原理,考虑形核和长大因素,建立了预测晶粒尺寸的理论模型,利用该模型对近液相线半连续铸造6061铝合金的晶粒大小进行了计算,所得结果与实验吻合.在所计算的几个条件中,最大误差小于7μm.通过对凝固过程中液固界面法向生长的扰动分析,得出球形晶粒周边主导波长及对应于一定波数的临界晶粒直径表达式.利用此关系可以很好地解释球晶生长及其向一定形貌的枝晶转变的条件及机理;对于分析凝固组织中不同形貌晶粒的形成及演化具有参考价值;对于半固态合金组织性能预测及其制备工艺优化具有实际意义.更多还原

【Abstract】 A theoretical model on the grain size prediction was established according to the thermodynamics of the alloy solidification and consideration on the factors of the nucleation and grain grow th.The grain size of the near liquidus semicontinuous casting 6061 aluminum alloy w as calculated by using the model.The calculated results are w ell consistent w ith the experimental ones w ith the maximum error less than 7 μm.Through the analysis of the grow ing disturbance along the normal direction to the liquid-solid interface during the solidification,a equation of the critical grain diameter corresponding to a certain w ave number and the dominant w avelength surround the spherical grains w ere obtained.The spherical grain grow th and its transformation conditions and mechanism of dendritic grains w ith specific type w ere w ell explained by these expressions,w hich is of great significance to the study on the formation and evolution of the grains w ith different morphologies,and to the prediction of microstructures and properties of semisolid alloy as w ell as the processing optimization.更多还原