Tailoring elastic modulus and mechanical biocompatibility of β Ti–33Nb–33Zr alloy via casting, hot rolling, and ECAP processing

Abstract β -Type titanium alloys are highly attractive for biomedical applications due to their low elastic modulus (50–80 GPa), high mechanical strength (500–1000 MPa), and excellent biocompatibility with bone tissue and physiological fluids. However, a major challenge in this field is achieving an optimal balance between mechanical strength and elastic compatibility with bone through controlled thermomechanical processing. In particular, the influence of severe plastic deformation techniques on the microstructure and mechanical behavior of multicomponent β –Ti alloys remains insufficiently understood. In this context, this study investigates the effects of melting, hot rolling, and Equal Channel Angular Pressing (ECAP) on the microstructure and mechanical properties of the β –Ti–33Nb–33Zr alloy. The alloy was synthesized by arc melting, hot rolled, and subjected to ECAP at 25 °C and 350 °C with different numbers of passes. Microstructural analyses (OM, SEM, TEM, EBSD, ASTAR) revealed that rolling promoted dynamic recrystallization, while ECAP significantly refined grains, particularly after two passes. At 25 °C, ECAP produced high dislocation densities and subgrains, whereas processing at 350 °C favored dynamic recovery. Microhardness increased after rolling and stabilized with ECAP, reflecting the balance between grain refinement and stress relaxation. The elastic modulus (~ 80 GPa) remained stable across treatments due to the persistence of the β phase and unchanged alloy composition, remaining lower than that of conventional Ti alloys (~ 100 GPa). Overall, the results demonstrate that ECAP combined with controlled processing temperature can enhance the strength of β -Ti alloys while preserving their elastic compatibility with bone, highlighting their potential for biomedical implant applications. Graphical Abstract