Producing fine fully lamellar microstructure for cast γ-TiAl without hot working

Abstract

In this study, a fine fully lamellar structure was formed with only a stepped-cyclic heat treatment process without hot working. The cast structure before the heat treatment contained large segregation areas and a coarse columnar structure (>1000 μm). Thus, the mechanical properties at room temperature were not ideal. In contrast, the segregation in the microstructures after the heat treatment was mostly removed with the formation of the fine fully lamellar structure (>65 μm). The mechanical properties at room temperature were improved by the effect of the fine fully lamellar. A room temperature tensile test was conducted to evaluate the mechanical properties of the controlled microstructure. As the fully lamellar structure became fine, the yield strength at room temperature increased from 482 MPa to 650 MPa and the total strain increased from 0.3% to 0.71%.