Tailoring Layered Structure and Tensile Properties of High-Nb TiAl Alloy Fabricated by Electron Beam Melting: Role of Line Offset and HIP

Abstract

A high-Nb TiAl, Ti-47.5Al-7Nb-0.2W was fabricated by electron beam melting (EBM) with varying line offset. Defects, microstructure and tensile properties of as-built and hot isostatic pressing (HIP) materials were studied. For the first time to our knowledge, we reveal that the layered structure in EBM TiAl forms because of the preferential coarsening of γ grains in Al-rich regions during HIP. A smaller line offset leads to more Al evaporation, fewer coarsened grains and therefore higher strength, with yield strength reaching 776 MPa when line offset is 0.15 mm (HIP material). Dislocation glide and twinning are the main deformation modes; twin intersection and blocking of dislocation by twins are found to strengthen the alloy. The present alloy outperforms existing cast/EBM TiAl alloys (e.g., TiAl 4822) across temperatures (25–850 °C), demonstrating potential for high-temperature aerospace applications.