Study on Uniformity of Microstructure and Anisotropy of Mechanical Properties of TC4 Titanium Alloy Sheets with Two Microstructures

The effects of rolling processes on the microstructure and mechanical properties of TC4 titanium alloy sheet are studied. The results indicate that the lamellar microstructure consisting of lamellar α and residual β phases is obtained by β phase field deformation, and that the equiaxed microstructure consisting of equiaxed α, lamellar α and residual β phases is obtained by α+β phase field deformation. The mechanical test results show that the match between the strength and plasticity of TC4 sheet with equiaxed structure is better than that with lamellar microstructure, while the impact and fracture toughnesses of TC4 sheet with lamellar structure are better. The uniformity of microstructure and mechanical properties of TC4 sheets with the two microstructures is further analyzed. The results indicate that the microstructure and mechanical properties along the normal direction(ND) of two types of TC4 sheets show higher uniformity, and that the anisotropy of tensile strength and fracture toughness in the sheets along the rolling direction (RD) exists. The texture of <0001>α//TD direction in the TC4 sheet would increase the slip resistance of dislocations in the transverse direction (TD), resulting in higher strength in the TD than in the RD. There is obvious flowline microstructure along the RD in the TC4 sheet, which increases the resistance of crack transgranular propagation, resulting in higher impact and fracture toughnesses in the TD-RD direction than those in the RD-TD direction.