Quantitative strengthening evaluation of powder metallurgy Ti–Zr binary alloys with high strength and ductility

Highlights:• Ti–Zr sintered alloys fabricated from pre-mixed Ti and ZrH₂ powders.• Uniform solution of Zr in α-Ti matrix by homogenization and water-quenching.• Ti–Zr alloys consisted of the equiaxed fine α-Ti grains.• Zr solid solution and α-Ti grain refinement were main strengthening factors. -- Abstract: Titanium is well-known for its high strength, good corrosion resistance, and biocompatibility. For further improvement of its mechanical properties, it is alloyed with other elements, such as zirconium. In this study, pre-mixed pure Ti powder and ZrH₂ particles were employed to prepare extruded Ti–Zr alloys with a low hydrogen content via dehydrogenation after sintering. The Zr solutes were uniformly dissolved in the α-Ti matrix by applying the optimal conditions for homogenization and water-quenching heat treatment. The synthesized Ti–Zr alloys consisted of the equiaxed fine α-Ti grains via dynamic recrystallization during extrusion. When the ZrH₂ particle content was less than 10 wt%, the extruded Ti–Zr alloys showed a large tensile elongation of more than 25% at room temperature with a yield stress of approximately 850 MPa. In the case of Ti–10% ZrH₂ powder, the mean α-Ti grain size was 2.7 μm, which was smaller than that of extruded pure Ti (3.5 μm). By applying the Hall–Petch equation for grain refinement and Labusch model for Zr solid solution to quantitatively estimate the increase in the yield stress, it was clarified that both factors had an equal effect for Ti–5 and –10 wt% ZrH₂ powder even with the dominance of solid-solution strengthening by Zr solutes for alloys with small Zr content.