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摘要
In order to obtain fine-grained TiAl alloy and effectively reduce internal defects caused by traditional casting, in this paper, the Ti-44Al-2Cr-4Nb-0.2W-0.2B alloy was prepared by vacuum hot pressing sintering process, and the effect of sintering temperature on the microstructure and mechanical properties of TiAl alloy was studied. The results show that according to Ti and Al element powder reaction synthesis mechanism, the alloys sintered at three temperatures (1150, 1240, 1300 ℃) are mainly composed of γ and α2 phases after XRD inspection. With the increase of sintering temperature, the content of γ phase increases, and that of α2 phase decreases. Combined with SEM observation, it is found that different typical structures of TiAl alloy can be obtained by changing the sintering temperature. The sintered alloy at 1150 ℃ with a near-gamma structure, at 1240 ℃ with a dual-state structure, and at 1300 ℃ with a near-lamellar structure, the microstructure becomes more uniform with the increasing sintering temperature. With EDS analysis, the density of the alloy increases gradually and the diffusion of Nb element in the matrix phase is promoted with the increasing sintering temperature. When the sintering temperature rises to 1300 ℃, the density of the alloy reaches to 4.419 g/cm3. Through mechanical property testing, the TiAl alloy sintered at 1240 ℃ shows better comprehensive mechanical properties with a microhardness of 5270 MPa at room temperature and good compressive strength at high temperatures.
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