Magnetic and acoustic techniques for determining the phase composition and destruction dynamics of plastically deformed cobalt-free martensite-aging steel

Abstract

The results of investigating the magnetic properties and phase composition (using the X-ray diffraction method) of specimens of cobalt-free ChS5VI (03N18M3TU) martensite-aging (maraging) steel that were subjected to a plastic tensile deformation are presented. It was established that all of the studied specimens can be divided into two groups depending on their heat treatment: specimens that were aged at T 550°C, in which the magnetic properties and the phase composition abruptly change at the initial deformation stages (up to 4–6%). The phase composition (the content of the residual austenite) in specimens of both groups, regardless of their degree of deformation, can be tested on the basis of the saturation induction and the N′ parameter, which correlates with the internal demagnetization factor. The acoustic-microscopy method showed that in specimens with the highest content of residual austenite, microflaws with minimum dimensions occurred during deformation, and cracks were not observed up to the specimen rupture. The location of the future neck nucleation at early deformation stages was predicted on the basis of acoustic images of subsurface layers for a specimen that was aged at T = 580°C.