Microstructure, texture and tensile properties of Ti-47Al-2Cr-2Nb alloy produced by selective electron beam melting

摘要

A Ti-47Al-2Cr-2Nb alloy was fabricated by selective electron beam melting, and the influence of energy density on porosity, microstructure, texture, Schmid factor and tensile property was investigated systematically. As the energy density increased continuously, the microstructure in the vertical cross-section transformed from fine-equiaxed grains with a low aspect ratio and a weakly crystallographic texture to elongated grains with a strong texture. The angles between the lamellar planes and the building direction accumulated 0 +/- 5 degrees and 45 +/- 5 degrees preferentially with the increase of energy density. Additionally, the average value of Schmid factor increased gradually from 0.39 to 0.45 with the enhancing energy density. The tensile properties of as-built samples produced at different energy densities were tested and the reason for the difference in tensile properties at different energy densities was explained. The formation mechanism of the preferred lamellar orientation that was fabricated at a high energy density was discussed in detail. The findings provide a valuable reference to fabricate TiAl alloy parts with a desired lamellar orientation, texture and tensile properties by tuning energy density during the selective electron beam melting process, and will be of significant interest for future applications. (C) 2018 Elsevier B.V. All rights reserved.