High-throughput guided heterostructured interlayer design for strength-ductility synergy in laser powder bed fusion TA15/Ti60 dual-material titanium alloys

When TA15/Ti60 dual-material gradient titanium alloys are fabricated by laser powder bed fusion (LPBF), abrupt changes in composition and microstructure at the bonding interface tend to cause poor interfacial bonding quality. In this study, an interlayer design strategy was proposed to improve interfacial properties. Furthermore, two sets of LPBF powder spreading auxiliary devices were designed for fabrication of high-throughput interlayer screening and dual-material samples with interlayer. The dual-material samples with interlayer exhibited a tensile strength of 1059.6 MPa and an elongation of 7.9%, respectively, which were significantly higher than those of the samples without interlayer, 646.5 MPa and 0.9%. The interlayer not only relieved the mismatch in microstructure and residual stress, but formed a heterogeneous microstructure consisting of ‘coarse reticular α + fine cluster α’, which achieved excellent strength-ductility synergy. The deformation incompatibility between the ‘coarse reticular α’ and ‘fine cluster α’ produced hetero-deformation induced (HDI) strengthening. Meanwhile, the extensive activation of < c + a > slip, twinning induced plasticity (TWIP), and the precipitation of (Ti, Zr)6Si3 jointly promoted the strength-ductility synergy. This study provides a new idea for strength-ductility synergy at gradient alloy interlayers, and proposes the simple and efficient LPBF auxiliary powder spreading strategy for fabrication of dual-material gradient alloys.