Influence of heat treatment on microstructure and tensile properties of conventionally cast and directionally solidified superalloy CM247LC

The influence of heat treatment on the evolution of γ′ and tensile properties of the conventionally cast (CC) and the directionally solidified (DS) superalloy CM247LC has been extensively investigated. The tensile strength of the CC and the DS alloys is dependent upon aging and solution treatment condition. In the case of the CC specimen, the aged condition (HTA condition) has higher strength than the solution treated and aged condition (HTSA condition) at low temperature (at and below 650 °C). On the contrary, HTSA specimen shows higher strength at high temperature (at and above 871 °C). Shearing of γ′ by coupled dislocations is a principal deformation process at the low temperature, and cutting of fine secondary γ′ plays an important role at an early stage of deformation in the CC specimen. The HTSA condition exhibits higher strength than HTA condition in the DS specimen in all temperature range. High tensile strength of the HTSA specimen at high temperature is found to be attributed to the rafting of γ′.