Effect of Y Addition on Microstructure and Mechanical Properties of TiAl-based Alloys Prepared by SPS

Abstract:

TiAl alloys with a composition of Ti-45Al-2Cr-2Nb-1B-0.5Ta(at%) (TA alloy) and Ti-45Al-2Cr-2Nb-1B-0.5Ta- 0.225Y(at%) (TAY alloy) were prepared by double mechanical milling and spark plasma sintering (SPS). The effect of Y addition on microstructure and mechanical properties of TiAl-based alloys was studied. The results show that the morphology of double mechanical milling powder is regular with sizes in the range of 20~40 μm. The main phases of TiAl and Ti3Al and few phases of Ti2Al and TiB2 were observed in the SPS bulk samples of TiAl-based alloys. The equiaxed crystal grain microstructure was achieved with sizes in the range of 100~400 nm in TA alloy samples. The samples exhibited compressive properties at room temperature with a compressive strength of 2614 MPa and a compression ratio of 20.57%. For TAY alloy, the sizes of equiaxed crystal grain obviously decreased. The samples exhibited compressive properties at room temperature with a compressive strength of 2677 MPa and a compression ratio of 22.91%. The micro-hardness of the SPS bulk samples of TA alloy was obviously higher than that of the SPS bulk samples of TAY alloy. On the base of analysis of fractographs, it showed that the compression fracture transform of the SPS TiAl-based alloys samples was intergranular rupture

Key words:TiAl-based alloys; spark plasma sintering (SPS); microstructure; mechanical properties; fractography