Microstructure And Mechanical Properties Of TiAl Alloy Prepared By Spark Plasma Sintering

?-TiAl based alloys are highly promising for elevated temperature structural applications in aerospace and automotive industries and are hopeful to replace Ni-base superalloy, which is widely used. This is due to their attractive properties, such as good elevated temperature strength, high resistance to oxidation, excellent creep properties and low density. However, the low room temperature ductility and poor deformability restrict their applications. In this work, several kinds of TiAl alloy were synthesized by Spark Plasma Sintering(SPS). In these alloys, Ti-44Al-3Nb-1Mo-1V-0.2Y was sintered by prealloy powders, and Ti-46Al-2Cr-0.5Si-0.2C, Ti-46Al-9Nb-0.5Si and Ti-46Al-9Nb-1Cr were sintered by element powders, respectively. A systematic study was carried out on the relationships among the parameters of SPS and powders, microstructure, room temperature compressive properties of the materials.Ti-44Al-3Nb-1Mo-1V-0.2Y alloy was sintered by pre-alloyed powder. Microstructure evolution of Ti-44Al-3Nb-1Mo-1V-0.2Y is affected by sintering parameters. When the sintering duration is 2 minutes, the microstructure exhibits duplex. When the temperature rises to 1200?, the microstructure shows fully lamellar. If the temperature increases further, the lamellar colonies become coarsening. When sinterd at 1100?,the alloy shows the best integrate mechanical properties, however, the alloy sintered at 1200? exhibits the highest strength.After the appearance of liquid aluminum, the reaction between elements occurs. The Ti-46Al-2Cr-0.5Si-0.2C alloy shows the typical duplex microstructure. With the increase of sintering temperature and duration, the proportion of lamella increases. The alloy sintered at 1350? for 5min with fine microstructure, shows relatively best integrate mechanical properties. With the increase of temperature and duration, the microstructure becomes coarse and correspondingly, the mechanical properties decrease.In the study of high Nb-TiAl alloys, Nb powders with different sizes were used. In Ti-46Al-9Nb-0.5Si alloy, Nb powder diameter was less than 38 ?m. After sintering at 1300? for 15 minutes, the uniform distribution of Nb is not attained, but a coarse microstructure appeares. With the action of Nb, B2 phase is appeared. In the Ti-46Al-9Nb-1Cr alloy, Nb powder less than 5 ?m was used to investigate the effect of particle diameter on its uniform diffusion. After sintering at 1300? for 5 minutes, the homogenization of Nb was achieved., with the phase constituent of ?, B2 and ?2. Compared with the Ti-46Al-9Nb-0.5Si alloy, the Ti-46Al-9Nb-1Cr alloy exhibits higher strength, due to its fine microstructure.