连续凝固偏晶合金薄带凝固组织进化过程模拟

分析了偏晶合金薄带垂直连续凝固过程,发展了描述该条件下偏晶合金凝固组织演变的数学模型,将计算的温度场和浓度场与凝固组织演变的控制方程相耦合,模拟了Al-5Pb(质量分数．%)合金的凝固过程．结果表明．在固/液界面前存在一过冷区、弥散相液滴在此区间内形核,这些液滴在移向凝固界面的过程中进行扩散长大,随着凝固速度的提高,形核率升高,弥散相液滴的数量密度增大．平均半径减小。

MODELING OF THE MICROSTRUCTURE EVOLUTION OF A STRIP CAST IMMISCIBLE ALLOY

The solidification process in a vertical strip cast immiscible alloy has been analyzed and a model describing the microstructure evolution has been presented. The solidification of the strip cast Al-5Pb (mass fraction,%) alloy has been simulated by coupling the calculated temperature and concentration fields with the kinetic equation which controls the microstructure development. The numerical results show that there exists an undercooled region in front of the solid/liquid interface and the minority phase droplets nucleated there. The droplets grow by diffusion of solute in the supersaturated matrix as they move toward the solid/liquid interface. A higher solidification velocity leads to a higher supersaturation and, therefore, a higher nucleation rate of the minority phase droplets. Thus, the number density of the minority phase droplets increases and the average droplet radius decreases with increasing the solidification velocity.