γ-TiAl Based Alloy Prepared By Ti And TiAl₃Reaction Sintering

TiAl based alloys have been taken seriously attention by the researchers at home andabroad, because of its low density, high specific strength and excellent high temperatureproperties and so on. The main methods to prepare TiAl based alloy by powder metallurgy areTi and Al elements powder sintering and pre-alloying powder metallurgy, respectively. Inorder to avoid the bulk expansion occurred in the elements powder sintering process and thehigh cost of the pre-alloying powder metallurgy. In this paper TiAl based alloys wrer preparedby Ti and TiAl₃reaction sintering through vacuum sintering and spark plasma sintering （SPS）.The influence of experimental parameters on structure and properties of sintered TiAl alloyshad been studied.Experimental results showed that the sintered TiAl alloy consists of γ-TiAl₂-Ti₃Al.Bulk expansion of samples was small. It is indicated that this reaction sintering avoids volumeexpansion occurred in the sintering process of elemental powders. After vacuum sintering, therelative density of samples was less than75%, improved a little coMPared to that of greenbody’s. The hardness of sintered samples was less than50HRB.Samples prepared by spark plasma sintering were composed of γ-TiAl and2-Ti₃Al. Ahigh density of3.84g/cm3was obtained. The relative density reached to98%. The hardness ofsamples was38.5⁴4.5HRC. Compressive strength at room temperature and bending strengthreached1717²102MPa and317³52MPa, respectively. After sintering at1100℃, theoptimal comprehensive performance was obtained. amples were of2102MPa powder that Tiand TiAl₃molar ratio is2:1mixed uniformly were spark plasma sintered, to study theinfluences of the sintering temperature on alloys’ composition microstructure and mechanicalproperties. At1050℃, the samples’ density is lower, the reaction phase are γ-TiAl in majorand2-Ti₃Al in minor, with some un-reacted intermediate phase TiAl₃and TiAl₂, withtemperature improved, the intermediate phase reduced. At1100℃, the density of samples washigher than3.84g/cm3. The hardness was42.7HRC. A compressive strength at roomtemperature of2102MPa and the compressive strain of24.12%were gained. The bendingstrength of samples sintered at1100℃was348.6MPa.