Enhanced strength and strain hardening in a dilute Ti-Ru alloy for load-bearing applications

Ruthenium (Ru) is often added to Ti alloys to enhance corrosion resistance, and due to its inherently high hardness, dilute Ti-Ru alloys could have both high strength and excellent corrosion resistance, which are appealing properties for load-bearing biomedical applications. However, limited knowledge exists regarding the microstructures, mechanical properties, and deformation mechanisms of Ti-Ru alloys. In this study, a Ti-1.5Ru at.% alloy with a duplex microstructure consisting of α blocks embedded within a matrix containing α′ martensites and retained β was prepared. Microstructural analyses confirmed that both α blocks and α′ martensites maintained the classical Burgers orientation relationship with the retained β. Nanoindentation experiments demonstrated higher hardness in the α blocks than in the matrix regions. Room-temperature tensile tests revealed excellent mechanical properties, including Young's modulus of 98 GPa, yield strength of 987 MPa, ultimate tensile strength of 1237 MPa, and significant strain hardening, resulting in 5.7 % uniform elongation. The high strength of this Ti-1.5Ru alloy can be attributed to the refined duplex microstructure, while the dislocations in the α blocks, along with stress-induced α′ and α″ martensites in the retained β, contributed to the observed strong strain hardening. This study sheds light on the potential load-bearing biomedical applications of high-strength dilute Ti-Ru alloys, offering microstructural robustness and promising mechanical performance.