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Alpha Phase Precipitation in Ti Alloys with Omega Phase Suppressor

Abstract

Metastable beta Ti alloys are applied in a number of sectors and obtained when enough beta stabilizer contents are added to Ti, which leads to a decrease in the beta transus temperature, shifting the martensitic transformation start temperature to below room temperature. When solution heat treated at high temperatures and rapidly cooled, they show metastable retained beta phase combined with omega phase, which is brittle, but it is essential in heterogeneous nucleation of alpha phase. An alternative to control omega phase precipitation in Ti alloys refers to addition of Sn or Zn. This research aims to investigate heterogeneous nucleation in Ti alloys with omega phase suppressors during aging heat treatments involving controlled heating to intermediate temperatures. Samples of Ti alloys with Nb, Sn and Zr alloy will be prepared by arc melting and then plastically deformed, solubilized and aged. These samples will be evaluated by optical microscopy, scanning electron microscopy and X-ray diffraction. The mechanical behavior will be evaluated by means of elastic modulus, Vickers hardness and tensile tests. It is expected to understand the effect of omega phase suppressors during aging heat treatments on the microstructure and mechanical behavior of metastable beta Ti alloys. (AU)