Tailored Fully Lamellar Microstructure of a Newly Developed Mn-Containing β-Solidifying γ-TiAl Alloys Rolled Bar

A low-cost Mn-containing β-solidifying γ-TiAl alloys Ti-44Al-4Mn-0.8Mo-0.1B-0.1C (at.%) alloy (named as TMM alloy) was invented. Rolled bars with a diameter of 12 mm were fabricated by conventional hot rolling, which was carried out directly from the ingot without the pre-forging and near-isothermal canned conditions. The microstructure and mechanical properties of as-rolled and heat-treated alloy bars were investigated. The rolled microstructure consists of a small amount of α2/γ lamellar structure, while plenty of fine-grained γ and βo phases at colony boundaries. The tensile properties at room temperature were obviously improved after hot rolling by refined microstructure. At 800°C, the plastic elongation can reach as high as 80.0% but with 452 MPa tensile strength due to the high amount of γ and βo phase at colony boundaries. The fully lamellar microstructure can be tailored via two-step heat treatment including solution and aging treatments. At 800°C, the tensile strength, elongation, and reduction of the area were 709 MPa, 4.5%, and 7%, respectively, which was much higher than the available wrought TiAl alloys. This study serves as a completely new low-cost β-solidifying γ-TiAl alloy which can be continuously hot-rolled under conventional conditions.