Research On The Effects Of Rare Earths On The High Temperature Oxidation Resistance Of Tial Based Alloys

Due to its excellent properties, such as low density, high specific strength and high specific elastic modulus, excellent creep resistance and oxidation resistance, TiAl based alloy has become one of the most promising high temperature materials used in aerospace engines and car components, which requires lightness and heating resistance. However, its fatal defect of low room-temperature plasticity and weak oxidation resistance exposed in high temperature prevents it from being widely used.At present, introducing alloy elements has become an important method to improve TiAl alloys'microstructure and properties. Alloying elements have great influence on the properties of TiAl based alloys. This paper will mainly discuss how rare earth (RE) element Y affects microstructure and high temperature oxidation resistance of TiAlNb alloys. It also discusses the oxidation mechanism, factors influencing oxidation resistance and improving methods.In this experiment, we investigated the alloys by means of optical microscope, XRD,SEM,EMPA and XRF. It revealed that, adding rare earths can obviosly refine the grain size of Ti-23Al-25Nb and Ti-45Al-5Nb alloys, and promote the formation of equiax crystals. We also find that in Ti-23Al-25Nb-0.3Y alloy, the rare earth-riched phases mostly enrich both at grain boundaries and inside grains in the shape of particles, phase analysis indicates that the rare earth-riched phases Y2O3 intermetallics. But in Ti-45Al-5Nb-0.3Y alloy, the most of rare earth-riched phases are uniformly distributed on grain boundaries in the shape of discontinuous networks, and some particles of the rare earth-riched phases are distribute inside grains, phase analysis indicates that the rare earth-riched phases are YAl2 intermetallics.From the oxidation surfaces, it was found the addition of Y promoted the uniformity of the surfaces and refined the grain size. As for Ti-23Al-25Nb alloys, the oxidation on the boundaries is worse than inside grains, and from the oxidation section we can also find that the oxidation rule is cyclic, and Y made the adhesiveness between oxide and matrix better and the thickness thin.The cyclic oxidation experiments at high temperature revealed that, the...