Abstract:A fine-grained TiAl alloy with a composition of Ti-47%Al(mole fraction) was prepared by double mechanical milling(DMM) and spark plasma sintering(SPS). The relationship among sintering temperature, microstructure and mechanical properties of Ti-47%Al alloy was studied by X-ray diffractometry(XRD), scanning electron microscopy(SEM) and mechanical testing. The results show that the morphology of double mechanical milling powder is regular with size of 20−40 μm. The main phase TiAl and few phases Ti₃Al and Ti₂Al were observed in the SPS bulk samples. For samples sintered at 1 000 ℃, the equiaxed crystal grain was achieved with size of 100−250 nm. The samples exhibited compressive and bending properties at room temperature with compressive strength of 2 013 MPa, compression ratio of 4.6% and bending strength of 896 MPa. For samples sintered at 1 100 ℃, the size of equiaxed crystal grain was obviously increased. The SPS bulk samples exhibited uniform microstructures, with equiaxed TiAl phase and lamellar Ti₃Al phase were observed. The samples exhibited compressive and bending properties at room temperature with compressive strength of 1 990 MPa, compression ratio of 6.0% and bending strength of 705 MPa. The micro-hardness of the SPS bulk samples sintered at 1 000 ℃ is obviously higher than that of the samples sintered at 1 100 ℃. The compression fracture mode of the SPS TiAl alloy samples is intergranular fracture and the bending fracture mode of the SPS TiAl alloy samples is intergranular rupture and cleavage fracture.

Key words: TiAl alloy; spark plasma sintering (SPS); microstructure; mechanical properties