基于经典动态模型的GH4169合金钢锭中Laves相的回溶规律分析

INVESTIGATIONS ON DISSOLUTION MECHANISM OF LAVES PHASE IN GH4169 ALLOY INGOT BASED ON CLASSICAL DYNAMICAL MODEL

在经典沉淀相回溶过程扩散动力学的基础上,结合商业软件Thermo-Calc中镍基合金各元素的热力学数据库及Dictra中的动力学数据库,在Matlab平台上开发了基于经典动态模型的沉淀相回溶及析出计算的原型系统,建立了镍基高温合金沉淀相回溶过程的经典动态模型.利用该模型计算了GH4169合金钢锭中不同尺寸Laves相的溶解量随时间和均匀化温度的变化,并与不同冷速下得到的凝固重熔铸锭均匀化前后的Laves相实际尺寸和体积分数进行对比分析.结果表明,利用经典动态模型计算的GH4169合金钢锭中不同尺寸Laves相的溶解量随时间和均匀化温度的变化与实验结果基本一致,说明该经典动态模型的预测结果可以作为工程应用中确定GH4169钢锭中Laves相回溶过程均匀化工艺的依据.

It is an urgent thing how to control the quality of large size GH4169 ingots nowadays. The high Nb element content in this alloy can increase the tendency of freckle defect formation. Though almost all the investigators consider that the segregation of Nb-riched Laves phase is the key factor of the freckle defect, how to avoid this phenomenon is still a hard-to-solve problem in engineering practice. In this work, a new prototype system based on classical dynamical model related to basic metallurgy theory was established to simulate the dynamical dissolving process of precipites evolution in nickel base superalloys. In this prototype system, the parameters related to the thermodynamic equilibrium state can be got from thermodynamic software of Thermo-Calc, the solute element diffusion coefficient at any temperature and time iterative can be got from dynamic software of Dictra. By using this prototype system, the dissolution process of Laves phase during homogenization process with different initial particle sizes for GH4169 alloy was simulated, and then series remelting experiments with different cooling rates and different Laves phase distributions were carried out, and the calculated results were in good agreement with the experimental results. This newly developed prototype system may give great help to homogenization process design in engineering use.