The effect of thermal history on elemental diffusion, phase evolution, and mechanical properties of laser powder bed fusion fabricated Ti6Al4V/AlMgScZr multi-material components

Abstract

Ti/Al multi-material components integrate the high specific strength of titanium with the lightweight characteristics of aluminum, demonstrating significant potential for applications in extreme environments. However, challenges such as weak interfacial bonding, elemental diffusion mismatch, and residual stress accumulation hinder broader application. In this study, Ti6Al4V/AlMgScZr multi-material components were fabricated using laser powder bed fusion (LPBF), with thermal history control to optimize residual stress and mechanical properties. The effects of thermal history on Ti/Al multi-material interface were analyzed, encompassing elemental diffusion, phase interface, and mechanical performance. Results showed that heat treatment significantly enhanced elemental interdiffusion, with the diffusion layer thickness increasing from 3.74 µm in the as-built state to 26.86 µm after 425°C× 4 h heat treatment. The L1₂-Al₃Ti phases formed a coherent interface with the aluminum matrix, alleviating lattice mismatch, enhancing stress transfer, and promoting partial ordered phases under high-temperature heat treatment. Simulations revealed that residual stress in the AlMgScZr region decreased from 282 MPa in the as-built sample to 81.2 MPa after heat treatment at 325°C× 4 h, effectively mitigating thermal mismatch-induced deformation and ensuring uniform stress distribution. This study provides new insights into the interfacial phase evolution and residual stress optimization in LPBF-fabricated multi-material systems. The synergistic effect of grain refinement and residual stress reduction led to a notable improvement in mechanical performance, with the tensile strength reaching 313.1 MPa after 325°C× 4 h heat treatment, representing a 50.3 % increase over the as-built sample. These findings offer valuable guidance for the design and processing of high-performance Ti/Al multi-material components for aerospace applications.