Microstructure Evolution during the Sintering of Blended Elemental Ti-23Nb-0.7Ta-2Zr-1.2O Gum Metal Alloy

Gum metal alloy Ti-23Nb-0.7Ta-2Zr-l .20 (%at.) was developed based on theoretical calculations to reduce titanium elastic modulus by the addition of β stabilizing elements Nb and Ta, and Zr to provide increased strength without unduly increase in elastic modulus. Gum metal alloy presents unique properties, differing significantly from β-Ti traditional alloys, and enabling a wide range of possible applications. The alloy can be highly cold workable without work hardening, resulting in an elastic modulus as low as 40 GPa and elastic deformation further than 2.5%, thus the name gum metal. This investigation aimed to fabricate the alloy by powder metallurgy and to evaluate the microstructure evolution after sintering from 700 to 1200 °C. Elemental powders of Ti, Nb, Ta e Zr were produced by hydriding followed by milling. Compaction of samples was carried out by uniaxial and isostatic cold pressing. Micro structural characterization was performed by scanning electron microscopy and mechanical characterization by microhardness test. Density evolution was determined by Archimedes method. The results demonstrate a tendency for the stabilization of a β-Ti microstructure from the dissolution of Nb and Ta particles (β-phase stabilizers). However, higher temperatures may be required to complete the dissolution of Nb and Ta nuclei.