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

A low-cost Mn-containing beta-solidifying gamma-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 alpha(2)/gamma lamellar structure, while plenty of fine-grained gamma and beta(o) phases at colony boundaries. The tensile properties at room temperature were obviously improved after hot rolling by refined microstructure. At 800 degrees C, the plastic elongation can reach as high as 80.0% but with 452 MPa tensile strength due to the high amount of gamma and beta(o) phase at colony boundaries. The fully lamellar microstructure can be tailored via two-step heat treatment including solution and aging treatments. At 800 degrees 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 beta-solidifying gamma-TiAl alloy which can be continuously hot-rolled under conventional conditions.