Abstract
Post-bond heat treatment (PBHT) applied to a transient liquid phase (TLP) bonding joint is an effec-tive approach to remove the brittle borides and improve its properties.Herein,we proposed two types of PBHT strategies to obtain a TLP bonded γ'-strengthened Co-based single crystal superalloy,and the microstructural characteristics and tensile properties of the two heat treated joints were compared to identify the optimal PBHT strategy.The evolution of the brittle boride in the joint after the PBHT was studied by using in-situ microscopy.The experimental results allowed to provide a theoretic model to quantitatively evaluate the distribution of the brittle phase after the optimal PBHT and analyze the joint fractures to understand the failure mechanisms.The obtained results revealed that a post-bond solid solution treatment performed to the joint at a high temperature (over 1275 ℃) could decrease the area fraction of the boride from 7.2 ％ to 1.4 ％ and increase the elongation from 1.9 ％ to 7.8 ％.This work emphasizes the relevance of solid solution temperature when a PBHT strategy is applied.
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