Research On Synthesis And Property Of The Ultrafine Grain And Nanocrystalline Ti-Al Alloy

Advanced design concepts tend to use the temperature higher, lighter and faster is the basis of the intermetallic compound TiAl-based titanium aluminide intermetallic compounds are most likely to meet the above design requirements, is considered to be the most application of a new generation of potential high temperature structural materials of light is expected in the aviation, automotive and other parts of the production has been widely used. Theγ-TiAl intermetallics at room temperature brittleness and the problem of insufficient high-temperature oxidation resistance, limiting its use and development. The purpose of this study is the use of powders by mechanical alloying and sintering, synthesis and preparation of ultrafine grain/nanocrystallineγ-TiAl organizations, and to study the performance of their organizations.Powder by mixing single-element test, the choice of TiH2, Al, Nb powder, prepared TiH2-47Al-(5-12) Nb alloy composition, formed by ball milling with amorphous, Ti2Al metastable nano-particle powder equivalent, with DSC and spark plasma sintering method, by different processes milled powder sintering and vacuum sintering to obtain ultrafine grained protection/nanocrystalline two-phaseγ-TiAl-based intermetallic compound TiAl Fund. By scanning electron microscopy, X-ray diffraction, transmission electron microscopy, differential thermal analysis instrument, such as observation and analysis of mechanical alloying and sintering of powder synthesis phase transition in the change process, the use of DSC controlled oxidation atmosphere, ultra-fine grain structure of TiAl high-temperature oxidation resistance.The results showed that:the synthesis of pre-milling of amorphous, nano-scale between the metastable phase TiAl is more conducive to the formation of ultrafine grain sintering/nanocrystalline bulk TiAl intermetallic compound. As the milled powders to retain some small Al element, while the lower melting point of Al, which occurs when the first liquid sintering, Al-proliferation and the formation of grain boundary phase connection strength. After 1200℃,10minafter sintering conditions, resulting in ultrafine grain/spherical nanocrystalline TiAl and Ti3Al. DSC sintering and spark plasma sintering were obtained with ultra-fine nanocrystalline grain structure, this fine grain structure with high temperature oxidation resistance. Alloy oxidation rate in air is far less than the oxidation rate in oxygen, Nb increases the amount of beneficial antioxidant activity increase. Confirmed by DSC cyclic oxidation temperature alloys, high temperature insulation and cooling stages of the oxidation reaction occurred, but the cooling stage of increase. Confirmed by DSC cyclic oxidation temperature alloys, high temperature insulation and cooling stages of the oxidation reaction occurred, but the cooling stage of oxidation was more evident.