Interfacial evolution and tensile deformation in LPBF Ti6Al4V/CuCrZr/CoCrMo laminated heterostructures: Effects of deposition sequence and heat treatment

Ti6Al4V/CoCrMo heterostructure alloys, which integrate bone-compatible properties with superior surface durability within a single component, exhibit significant potential for total hip replacement systems. However, the formation of brittle intermetallic compounds (IMCs) at the Ti-Co interface severely weakens interfacial adhesion and often leads to cracking. In this study, a CuCrZr alloy interlayer was introduced to mitigate thermophysical mismatch and improve interfacial formation between Ti6Al4V and CoCrMo fabricated by muti-materials LPBF. CFD simulations combined with interfacial microstructural characterization reveal that the Ti6Al4V→CuCrZr deposition sequence produces stable keyhole-mode melt pools with enhanced convective mixing and wider interfacial regions. In contrast, the CuCrZr→Ti6Al4V sequence induces turbulent flow and spattering due to severe thermal mismatch, resulting in narrower mixing zones and inferior bonding integrity. Furthermore, appropriate heat treatment reduces interfacial defects and promotes interfacial phase transformation, thereby improving load transfer and metallurgical compatibility. As a result, the elongation increases from 2.56% to 7.41%, while the ultimate tensile strength improves from 845.48 MPa to 973.03 MPa. The enhanced plasticity is mainly attributed to the alleviation of interfacial stress concentration and the activation of additional slip systems during deformation. These findings provide insights into interface regulation in LPBF-fabricated dissimilar metal systems and offer a feasible strategy for achieving reliable multi-material structures with large thermophysical differences.