Effects of Zr and Si addition on high-temperature mechanical properties and microstructure in Ti-10Al-2Nb-based alloys

摘要

The solid-solution strengthening effect for the single and simultaneous addition of Zr and Si on the compression strength and the creep property in Ti-10Al-2Nb based alloys (at%) with an equiaxed a phase designed by us, was investigated. The compression strengths of these alloys were investigated at temperatures between room temperature and 650 degrees C. The largest solid-solution strengthening effect was obtained for the alloys with Zr and Si simultaneously added, followed by alloys with the single addition of 2Zr or 0.5Si. For the same amounts of addition elements, the solid-solution strengthening effect of Si was larger than that of Zr. This was attributed to the larger atomic size misfit between Ti and Si than that of between Ti and Zr. A creep test was conducted for Ti-10Al-2Nb-2Zr and Ti-10Al-2Nb-2Zr-0.5Si within a temperature range of 550-650 degrees C under an applied stress between 137 and 240 MPa. The alloy with Si exhibited a longer creep life for all tested conditions due to a large solid-solution strengthening effect and high compression strength.The deformation mechanisms of the compressive deformation and tensile creep deformation were analyzed using an Arrhenius-type equation. Considering the stress exponent and activation energy, the deformation mechanism of the compressive deformation was identified as low-temperature power-law creep controlled by dislocation core diffusion. While, the deformation mechanism of the creep deformation was identified as high-temperature power-law creep controlled through lattice diffusion.