Microstructure and high-temperature tensile property of TiAl alloy produced by selective electron beam melting

Abstract

The microstructure and high-temperature tensile property of a Ti-47Al-2Cr-2Nb alloy fabricated via selective electron beam melting (SEBM) with hatch spacings of 85, 100, and 115 μm were systematically investigated. When the hatch spacing increased from 85 to 115 μm, the microstructure comprising the horizontal cross section changed from coarse lamellar (γ/B2) colonies to an inhomogeneous structure and the grain morphology transformed from elongated grains to inhomogeneous and equiaxed grains along the building direction of the vertical cross section. The boundary population of the SEBM-produced TiAl alloy samples was dominated by high-angle grain boundaries (≥ 15°), and the volume fraction of these boundaries decreased with hatch spacing increasing. Additionally, the as-built TiAl alloy sample produced under a spacing of 100 μm exhibited the highest room- and elevated-temperature tensile strengths, with the ultimate tensile strength at room temperature (642 MPa) increasing to 674 MPa at 700 °C. Furthermore, the mechanism of anomalous strengthening at 700 °C was discussed in detail.