Residual stress-free Laser Additive Manufacturing

Laser Powder Bed Fusion (L-PBF) is an enabling technique. L-PBF components occasionally show poor performance, which are originated from appreciable residual stresses introduced by solidification cycling. For steel, the volume expansion associated with displacive phase transformations provides a potential solution to mitigate residual stress development during initial manufacturing. However, multi-phase transformation phenomena cannot be fully evaluated by traditional a posteriori techniques due to their transient nature, necessitating in-situ characterisation. Here, it is proposed to use ID31’s high energy range to perform a three-step XRD study to understand the complex relationship between residual stress development and phase transformations in this manufacturing process. We will perform both ex-situ and in-situ synchrotron XRD on steels manufactured by L-PBF to elucidate and quantify the mechanism of residual stress reduction by phase transformations.