Computational modelling of the residual stress evolution due to solid-state phase transformation during welding

Ferrous weldments may experience solid-state phase transformation on cooling of austenite to martensite. It has been known that the volumetric change associated with the metallurgical phase transformation could have a major influence on the residual stress evolution. In this work, residual stress measurements were carried out to investigate the residual stress evolution due to the volumetric expansion in the weld and HAZ. Based on measurement results, this paper presents a three-dimensional one-way coupled thermal mechanical finite element model which takes into account the effects of solid-state phase transformation on residual stresses. Effects of variations in thermal and mechanical properties due to the phase transformation on the residual stresses are studied. The results show that the volumetric change due to the austenite to martensite phase transformation significantly affects the residual stresses in the transformation region, and the residual stress evolution is not mainly determined by the variation of specific heat but by that in specific volume in the phase transformation temperature range.