Thermomechanical Behavior and Experimental Study of Additive Manufactured Superalloy/Titanium Alloy Horizontal Multi-Material Structures

In laser powder bed fusion (LPBF) forming multi-material structures, the thermal stress mismatch caused by the different thermophysical properties of different materials can cause interface cracking and delamination defects. An in-depth investigation of the complex interfacial thermomechanical behavior caused by it is of great significance for reducing stress concentration, suppressing defects, and enhancing interfacial bond strength. In this study, the effects of scanning strategy and interface shape on the temperature distribution, thermal cycling, and thermal stress distribution at the interface are analyzed by the IN718-Ti6Al4V horizontal multi-material thermally coupled finite element model. The results show that the 45° scanning strategy is helpful for the uniform distribution of energy and the reduction of overheating and residual stress concentration. The maximum residual stress at the interface in the Ti6Al4V/IN718 structure is more than 700 MPa, which is higher than that in the IN718/Ti6Al4V structure. The first formation of Ti6Al4V will likely lead to higher residual stresses at the interface, which are difficult to release in subsequent printing. The analysis of different interface shapes shows that different interface shapes change the crack formation and extension paths. This study contributes to an in-depth understanding of improving the strength of horizontal multi-material interfacial bonding at the LPBF forming. It provides a reference for optimizing LPBF forming of difficult-to-bond materials.