Mechanical properties of porous metastable beta Ti–Nb–Zr alloys for biomedical applications

• Published in: Journal of alloys and compounds 2013-11, Vol.577, p.S413-S417
• Main Authors: Brailovski, V., Prokoshkin, S., Gauthier, M., Inaekyan, K., Dubinskiy, S.
• Format: Article
• Language: English
• Subjects: Alloys; Annealing; Biocompatibility; Foams; Ingots; Mechanical properties; Metals and alloys; Porosity; Powder metallurgy; Shape memory; Sintering; Surgical implants; Titanium
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2011.12.157

► Effect of cold rolling and annealing of Ti–Nb–Zr bulk alloys is studied. ► Effect of post-sintering heat treatment of Ti–Nb–Zr foams is studied. ► Cold-rolled and annealed bulk alloy with 100nm subgrain size is superelastic. ► Cold-rolled and annealed bulk alloy demonstrates high fatigue resistance. ► Ti–Nb–Zr foams show significant softening after post-sintering heat treatment. For this study, Ti–(20–22)Nb–(5–6)Zr (at%) ingots were manufactured by vacuum and argon arc melting. The obtained ingots were divided into two batches: the first subjected to cold rolling (CR) from 30 to 85% of thickness reduction, and subsequent annealing in the 450–600°C temperature range (1h). Regardless of the CR intensity, Ti–Nb–Zr samples subjected to 600°C annealing showed the highest fatigue resistance during room-temperature cumulative cycling due to the stress-induced martensitic transformation occurring in the polygonized dislocation substructure (average subgrain size∼100nm). The second batch was atomized to produce 100-μm-size powders in order to manufacture open-cell porous material (cell size vary from 136 to 561μm) of 46% porosity by means of powder metallurgy using a polymer-based foaming process. Tensile, compression and bending testing were performed at RT on foam samples annealed at 450–600°C (1h). Results indicated that Young's modulus of Ti–Nb–Zr foams significantly decreases as compared to the as-sintered material: when annealing temperature increases from 450 to 600°C, Young's modulus decreases from 10±2GPa to 6±1GPa. Under the same testing conditions, Ti-CP foams produced by the same technology and having similar porosity remain fairly insensible to post-sintering annealing.