Effect of silicon on creep properties of titanium 6Al-2Sn-4Zr-2Mo alloy

Abstract

The alloy Ti-6Al-2Sn-4Zr-2Mo is a titanium alloy for elevated temperatures often used in aerospace applications. Minor additions of silicon have proven to improve the creep resistance of this alloy. In this work, three different amounts of silicon (0.015, 0.07 and 0.162 wt% Si) were added to cast Ti-6242 and creep tests were performed at different temperatures and loads. Creep resistance increased significantly with silicon addition by means of silicide precipitation hindering dislocations movement. Silicon rich nanoparticles in the microstructure were detected and their effect on creep resistance was investigated. The instruments used in this study were light optical microscope (LOM) and scanning electron microscopy (SEM). Precipitates larger than 150 nm were found to be located heterogeneously in the microstructure, whereas smaller precipitates, ranging from 20-100 nm were homogeneously spread in the material. All silicides were predominantly situated next to the beta-phase in the alloy, either at the prior-beta grain boundaries or the beta-phase in between the alpha-colonies.