Microstructure and mechanical properties of Ti basic bionic gradient heterogeneous alloy prepared by multi-wire arc additive manufacturing

Abstract

Inspired by biological gradient structure, Ti basic gradient heterogeneous alloy component from TC11 alloy to TC4 alloy was fabricated by multi-wire arc additive manufacturing (MWAAM). The chemical mixing, phase and microstructure evolution, microhardness distribution and tensile property of Ti basic gradient heterogeneous alloy were investigated through EDS, XRD, SEM, hardness tester and tensile tester. The results indicated that the alloy elements formed a long-distance gradient concentration distribution during the transition between two different titanium alloys due to dilution, remelting, and convective mixing in the molten pool. The intensity of diffraction peaks of Ti basic gradient heterogeneous alloy in the gradient region had no obvious change. The microstructure of MWAAM Ti basic gradient heterogeneous alloy was mainly consisted of lamellar αP, acicular αS, equiaxed αS and β matrix. Different morphology of the αS phase was mainly attributed to the wetting state of the second solid phase and grain boundary. In addition, the microstructure of α phase in Ti basic gradient heterogeneous alloy was significantly changed by the gradient distribution of alloy composition. The gradient heterogeneous alloy component manufactured in this work had high bonding strength. The average UTS of MWAAM Ti basic gradient heterogeneous alloy was 793.14 MPa, which was close to MWAAM TC4 alloy and reached approximately 85% of MWAAM TC11 alloy.