Thermal features and residual stress evolution at the interface of Ti6Al4V/AlSi10Mg multi-material produced by laser powder bed fusion

Despite of the promising advantages of adopting laser powder bed fusion (LPBF) in forming of Ti/Al dissimilar material structure, the interfacial property has been one of the most critical challenges that hinder the development of this technology for further application in engineering fields. A fundamental understanding of the process-interfacial property relationships is crucial for process optimization and performance control of LPBF-formed dissimilar material parts. Different from the majority literature that focuses on the formation of pores and brittle microstructures at the interface zone, this work uniquely explores the thermal features and interfacial stresses (those are regarded as the main reasons of process failures and fractures) in LPBF forming dissimilar material parts and the influence of forming height on the residual stress distributions. A coupled thermo-mechanical model using the finite element method was proposed to simulate the residual stress distributions at the interfacial zone for several designed part parameters. A combined experimental and numerical study was conducted to record the interfacial stress field of different forming heights to reveal the mechanisms of stress evolution with heat accumulation. The numerical results show that the interfacial stress increased by at least 26 % as the forming height of AlSi10Mg doubled, while it decreased to 50 % with stress relieving treatment in Ti6Al4V. The presence of initial stress and heat accumulation both lead to uneven deformation at the interface zone, thus resulting in larger residual stresses.