Effect of Mn and Mo on the microstructure and electrical resistivity of Ti-Al alloy prepared by mechanical alloying and spark plasma sintering

Abstract

High electrical resistivity titanium alloys can effectively reduce the attenuation of eddy current shielding to magnetic field, and have a good application prospect in magnetic compression devices. The Ti-Al alloys alloyed with Mn and Mo were prepared by mechanical alloying and spark plasma sintering in this study. The effect of alloying elements Mn and Mo on microstructure characteristics, electrical resistivity and micro-hardness of Ti-Al alloy, as well as the effect of annealing on Ti-Al-Mn-Mo quaternary alloy were investigated. The results show that the microstructure of Ti-9Al-xMn (x = 0, 1, 2, 4, 6 wt%) alloys was transformed from a single-phase α of Ti-9Al alloy to multiphase consisting of α + β + α2 phases. With the increase of Mn content, the number of α phase decreased, and (β + α2) dual phase region increased. The electrical resistivity of Ti-9Al-xMn alloys increased with the increase of Mn content and decreased as Mn content was more than 4 wt%. The Ti-9Al-4Mn alloy had the electrical resistivity of 2.176 μΩ‧m. The α phase grains in Ti-8Al-4Mn-1Mo and Ti-7Al-4Mn-2Mo were refined by Mo alloying, the content of α2 phase reduced, and β phase increased compared with Ti-9Al-4Mn alloy. The electrical resistivity of the quaternary alloys increased and the micro-hardness decreased. The Ti-8Al-4Mn-1Mo alloy had the higher electrical resistivity (2.252 μΩ‧m) and micro-hardness (627 HV). Annealing slightly decreased the micro-hardness of Ti-8Al-4Mn-1Mo alloy, but the electrical resistivity remained at the level of as-sintered alloy.