Evolution of as-solidified and heat-affected microstructures under different thermal manufacturing processes for 316 L stainless steel

Abstract

In this study, laser-arc welding (LAW), laser welding (LW), and laser cutting (LC) of 316 L stainless steel plates were selected to comparatively study melting-solidifying and heat-affected zones (MSZ, HAZ). Variations of morphology, crystalline orientation, and phase interfaces were systematically investigated from LAW to LW and LC. In the MSZ, δ phase presented a dramatic decrease in fraction and size with degenerated dendritic and increasingly dispersed features while γ grains were gradually refined. Special orientation relationships Bain, K.-S., N.-W. and G.-T. were frequently observed in re-solidified zones and δ coarsening regions of HAZ. Depending on the solidification speed, temperature gradient, and solid/liquid interface instability caused by manufacturing processes, δ and γ refinements in MSZ and HAZ from LAW to LW and LC were attributed to the S/L instability, lowered high-temperature duration，and variable epitaxial growth on previously formed δ (LW) or γ (LC). • Evolution of microstructure and microtexture in as-solidified and heat affected zones were compared. • The fraction and arrangment of δ phase was primarily controlled by the solid precipitation duration. • Grain size and orientation of γ phase was both decided by previously formed δ phase at a low temperature gradient or γ phase at a high one.