Microstructure evolution and mechanical properties of TNM-0.9C alloy treated under different processing parameters
Feng Huang, Zihao Zhan, Shangxing Hu, Daoling Zhang, Yanxiong Liu, Zhili Hu, Lin Hua
Abstract
According to the differential scanning calorimeter (DSC) test results, the as-cast TNM-0.9C alloy was subjected to solid solution and subsequent aging treatment with different solution temperatures and same aging conditions. The microstructure and mechanical property evolution behaviors were characterized and measured, and the influence of solution temperature was discussed emphatically. The results indicate that α 2 /γ lamellar structures were formed after heat treatment. As the solution temperature increased from 1230 °C to 1400 °C, the relative contents of α 2 and B2 phases decreased from 17.2% to 3.7%–9.1% and nearly 0%, respectively, while that of γ phase increased from 79.1% to 90.9%. At the same time, the Ti 2 AlC phase gradually changed from slender rods to spheres until it was completely dissolved into the matrix. Solid solution and subsequent aging is proved to be effective in improving the mechanical properties of this as-cast carbon-containing TiAl alloy. However, too high solution temperature (such as 1400 °C) will make the alloy grains seriously coarser and produce a small amount of large size brittle B2 phase, both of which eventually deteriorate the mechanical properties of the alloy. The alloy treated with solution at 1300 °C and subsequent aging exhibited the best overall performance. Compared with the original as-cast sample, its tensile strength and strain at room temperature are increased by 77.7% and 38.3%, while the corresponding compressive strength and strain at high temperature (800 °C) are increased by 33.0% and 17.0%, respectively.