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

Abstract

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.