Ti-13Al-29Nb-2.5MoISM过程中Al元素的挥发损失速率

Evaporation rate of aluminium in Ti-13Al-29Nb-2.5Mo melt during induction skull melting (ISM) process

借助于Kohler三元溶液模型和Miedema二元溶液生长热模型 ,计算了Ti -1 3Al -2 9Nb -2 .5Mo合金中Ti、Al及Nb组元的活度系数 ,并在此基础上计算了合金中组元的平衡分压及Al元素的挥发损失速率 .结果表明 ,组元的活度系数、平衡分压及Al元素的挥发损失速率均随温度的升高而增大 .存在一个临界外压 (约为 1 3 3Pa) ,当外压大于此值 ,挥发损失速率急剧减小并趋于一稳定值 .这给合金熔炼过程中合金成分控制提供了理论指导 .

Based on Kohler′s ternary solution model and Miedema model for calculating the heats of formation - ΔH ij  of binary systems, the activity coefficients in Ti-13Al-29Nb-2.5Mo melt have been calculated. Taking advantage of the activity coefficients, the equilibrium partial pressures of elements in the melt and the evaporation loss rate of element Al have also been calculated. The calculation shows that the activity coefficients, equilibrium partial pressures and the evaporation loss rate increase with the increase of the temperature. When the chamber pressure(p) is above 133 Pa (which is called critical pressure), the evaporation rate of Al sharply decreases and declines to a constant consequently. Our theory gives useful guidance to the practical process of process melting alloy.