Influence of Cr content on phase constitution, electrical resistivity and vickers hardness in quenched Ti-Cr alloys

Abstract

As basic study to develop low cost βTi alloys, changes in phase constitution, electrical resistivity and Vickers hardness with increase of Cr content were investigated in Ti-Cr binary alloys quenched from 1173 K. In solution treated and quenched state, hexagonal martensite, α' was identified at 3Cr and 5Cr alloys, whereas β phase was identified from 5Cr to 20Cr. In 7Cr and 10Cr alloys, athermal ω was also identified. Resistivity increased with increase of Cr content up to 10 mass% Cr and then slightly decreased. Above 10 mass% Cr, resistivity at liquid nitrogen temperature was larger than that at room temperature. Maximum of HV appeared at 7 mass% Cr and then HV decreased with increase of Cr content up to 13 mass% Cr. Above 13 mass% Cr, HV slightly increased due to solution hardening by Cr addition. Temperature-resistivity curves of alloys from 10Cr to 20Cr were negative temperature dependence between 77 K and about 300 K. From change of the temperature-resistivity curves with Cr content, it is expected starting temperature of athermal ω formation decreases with increase of Cr content. Trend of changes in HV of Ti-Cr, Ti-Fe and Ti-V alloys as a function of e/a was the almost same, though absolute these values of the three alloys are not same.