Formation of Fine B2/β plus O Structure and Enhancement of Hardness in the Aged Ti2AlNb-Based Alloys Prepared by Spark Plasma Sintering

Ti2AlNb-based alloys synthesized at 1223 K (950 A degrees C) by spark plasma sintering were aged at 973 K, 1023 K, 1073 K, and 1123 K (700 A degrees C, 750 A degrees C, 800 A degrees C, and 850 A degrees C), respectively. Phase composition, microstructure, and microhardness of the aged alloys were investigated in this study. Equiaxed O grains and Widmanstatten B2/beta + O laths were formed in the aged alloys, and the microhardness was improved in contrast with the spark plasma-sintered alloy without aging. The microhardness relies largely on the O-phase content, as well as the length and width of the O laths. In particular, complete Widmanstatten B2/beta + O laths, with locally finely dispersed beta precipitates, were obtained in the alloy aged at 1073 K (800 A degrees C), and the alloy exhibited the best microhardness performance. Such fine structure is due to the temperature-dependent transformations O-equiaxed -> O-primary + B2/beta (primary), O-primary -> O-secondary + B2/beta (secondary), and B2/beta (primary)-> O.