Influence of chromium content on microstructure and grain boundary serration formation in a ternary Ni-xCr-0.1C model alloy

Abstract

The influence of chromium content on microstructure and grain boundary serration formation in a ternary Ni-xCr-0.1C model alloy was investigated. First, the cast alloys were hot-compressed and then solution treated to obtain a recrystallized structure. Second, a proprietary heat treatment was employed to all of the compressed alloys to produce the serrated grain boundaries. The recrystallization retardation of the alloys increased with increasing chromium content after the first step. This may be attributed to the change in lattice distortion due to the addition of chromium into the solid solution of the nickel matrix, and it was also affected by Zener drag pressure exerted by the formation of carbides suppressing the grain growth during solution treatment. Furthermore, the grain boundary serrations were found in all of the alloys after the second step. It was determined that the serrated grain boundary was initially formed without carbide formation during slow cooling. The formation of grain boundary serration is thought to be promoted by lattice distortional strain near grain boundaries due to discontinuous chromium segregation. The higher chromium content promoted a substantial increase in the lattice distortion energy, which resulted in a higher amplitude of the serrated grain boundary.