Influences of time and temperature on the microstructures of Ti48Al2Cr2Nb alloy diffusion bonded joints by spark plasma sintering

Ti-48Al-2Cr-2Nb (at.%) alloys were diffusively bonded using spark plasma sintering (SPS) with Ti/Ni/Ti foils as an interlayer. The results indicated that the mutual diffusion of the elements between the matrix alloy and the interlayer was limited at 950 °C with a holding time of 15 min. At the same temperature of 950 °C, the diffusion of the elements was improved with increasing the holding time to 30 min. At the same holding time of 30 min, the joints showed the similar microstructures consisting of α₂ phases as the main phases in each layer at the temperatures of 900 °C and 950 °C, while the α-Ti only formed in the inner layer. With increasing the temperature to 1 000 °C and 1 050 °C, the layers disappeared and the joints were characterized by coarsen α₂ phases and the α₂ phases with few solid solution Ni, Nb and Cr elements. SPS accelerated the diffusion of the elements in the joints, especially the Ni element, which inhibited the formation of TiNi and TiAlNi intermetallic compounds.