Achieving enhanced tensile strength-ductility synergy through phase modulation in additively manufactured titanium alloys

Abstract

The quest for titanium alloys with an optimal combination of tensile strength and ductility is paramount for their application in critical industries. Additive manufacturing (AM) offers a unique avenue to control the alloy's microstructure, thereby modulating its mechanical properties. This study presents a comprehensive investigation into the phase modulation strategies in AM-processed titanium alloys to achieve a synergistic improvement in tensile strength and ductility. The advancements in this work have enabled the progressive evolution of titanium alloy microstructures with addition of β stable elements, transitioning from near α-Ti alloys to α+β alloys, and finally to near β-Ti alloys. This approach has led to a significant enhancement in the tensile strength of as-prepared titanium alloys, complemented by a moderate retention of ductility. The primary contributors to this mechanical property improvement are identified as solid solution strengthening, grain refining strengthening, and grain boundary strengthening, all of which are facilitated by strategic phase modulation. Moreover, the generation of refined α lamellas, equiaxed α phases, and discontinuous grain boundary α phases has been shown to be instrumental in promoting coordinated deformation within the alloy, thus enhancing the overall ductility. Varying fracture modes demonstrated the potential of microstructure tailoring via multi-eutectoid elements alloying, facilitating the in-depth understanding of crack initiation, propagation, and strain-to-failure, shedding the lights on the enhancement of strength-ductility synergy.