Quantitative characterisation of last stage solidification in nickel base superalloy using enthalpy based method

Abstract

An enthalpy based method was used to determine the solidification characteristics in the Ni base superalloy IN713LC with the emphasis on the late stages of solidification. Solidification commences with freezing of γ-solid, which is followed by precipitation of carbides (MC) and subsequent divorced growth of MC and γ until solidification terminates. During solidification enthalpy change was measured using differential thermal analysis and latent heat was calculated using a multicomponent thermodynamic software database. The measured enthalpy and calculated latent heat were then used to determine liquid fraction evolution and local freezing rate. A quantitative comparison of calculated fraction liquid evolution and local freezing rate with those determined using equilibrium and Scheil approximations was carried out. The comparison reveals that the present method offers a more accurate approach for characterising the late stages of solidification than the equilibrium and Scheil models.