Acoustic methods for characterization of microstructures and deformation processes in nimonic alloy PE16

Abstract

Application of acoustic methods for characterisation of microstructures and deformation processes in high temperature nickel base superalloy, Nimonic alloy PE16 is reported. The ultrasonic velocity is found to depend on the type of phases present and it is possible, under certain conditions, to identify and therefore, control the heat treatment using velocity measurements. The velocity is found to vary linearly with volume fraction of γ'. The non-correlation between hardness and velocity at lower periods of ageing at 973 K has been attributed to the fact that hardness is a measure of resistance to deformation, a plastic property whereas velocity is related to elastic properties. Various acoustic emission parameters have been used to correlate the AE behaviour with particle shearing and Orowan looping processes taking place in presence of γ and decohesion and fracture of MC occurring during tensile deformation in Nimonic alloy PE16.