Effect of NbH Particle Size and Cooling Type on the Microstructure, Phase Composition and Microhardness of Ti-20Nb-20Zr Alloy

Titanium alloys are widely used as implants in orthopedics and dentistry due to their properties such as high strength, corrosion resistance, biocompatibility and good fatigue resistance. Alloys composed of non-toxic elements, like Nb and Zr, provide lowest Young’s modulus with values near to human bone modulus. The goal of this work was to study the effect of NbH particle size and cooling type on the microstructure, phase composition and microhardness of Ti-20Nb-20Zr alloy. The powders were produced by hydrogenation method. Two different powders of NbH were prepared: powders comminuted (C) and comminuted followed by milling (C+M). After, the alloy powders were milling and homogenizated for 6 h / 300 rpm and sintered at 1300 °C / 3h followed furnace cooling. Afterward, the specimens were treated at 1000 °C / 1 h and cooling in air and water. The samples were characterized by XRD, SEM and Vickers microhardness. The results showed that the alloy is classified as α + β. Vickers microhardness of Ti-20Nb-20Zr ranged between 680-700 and 540-600 HV from alloys prepared with NbH-comminuted and NbH comminuted + milled, respectively. Results indicated that NbH agglomerate behave as barriers for the sintering process of the alloy.