Simultaneous Residual Stress and Retained Austenite Measurement by X-Ray Diffraction

Abstract

A new fiber optic based XRD instrument is described that is capable of measuring simultaneously both residual stresses and phase composition present in steels. The hardening of steel requires that the material first be heated to a high enough temperature to produce a face-centered cubic polycrystalline solid solution called austenite. The material is then rapidly quenched to form a hard, metastable body-centered tetragonal solid solution called martensite. In practice, the transformation is incomplete, leaving some austenite at room temperature. Because the presence of austenite is often detrimental to the quality of the steel, it is of considerable interest to be able to quantitatively determine the amount of the austenite phase present (the retained austenite), as well as the amount of residual stress induced in the martensite.

This paper describes a new three detector XRD instrument that is capable of making simultaneous measurement of both residual stresses and retained austenite in steels at the same location on the sample in a few seconds.