A N NEW EW ANALYTICAL NALYTICAL METHOD OF γ / γ ’ MORPHOLOGYIN SINGLE CRYSTAL Ni Ni-BASE SUPERALLOYS:FOR NEW ORIENTATION OF DAMAGE AND REMAINING LIFE ASSESSMENT ASSESSMENT

摘要

This paper focused on γ/γ’ morphological changes in a singlecrystal Ni Ni-base superalloy, CMSX CMSX-4, induced by monotonicplastic strain straining ing and cyclic fatigue loading loadings. It was shown by a. series of experiments that an application of the monotonicstraining at R.T. and the subsequent h heat treatment at at hightemperature resulted in a directional coarsening ofγ/γ’microstructure, depending on the sign, magnitude and history ofstrain. A critical strain was found to be needed to build up themicrostructural changes. Not only monotonic but also cyclicload loadings could induce similar changes in the ingsγ/γ’ microstructures.These changes have been summarized in tables. In order toquantify theγ/γ’ morphologies, a new method, named by Cluster Cluster-Method, was proposed, where the degree of the coarsening andthe directi directional coarsening can be displayed on an original 2 onal 2-dimensional diagram. This method successfully evaluate evaluated varioustypes ofγ/γ’ microstructures. Furthermore, this method mayprovide us new potentials for both the stress field detection andthe remaining life analysis of superalloy components in service.