Effect of Microstructures on High-temperature Oxidation Behavior of TiAl Alloy
The constant-temperature oxidation behavior of TiAl alloys with different microstructures was systematically investigated at 850℃,and the high temperature oxidation mechanisms were revealed clearly.The results indicated that TiAl alloys with near-γ and dual-phase microstructures exhibited excellent high-temperature oxidation resistance.After oxidation at 850℃for 100 h,the thickness of oxide film on the surfaces was 13.78 μm and 12.81 μm for the near-γ and dual-phase TiAl alloys respectively.While the TiAl alloy with fully lamellar microstructure showed an oxide film thickness of 19.06 μm under the same conditions.After oxidation at 850℃for 100 h,non-protective TiO2/Al2O3 mixed layers formed for all TiAl alloys with different microstructures.The inadequate high-temperature oxidation resistance of TiAl alloy with fully lamellar microstructure was mainly attributed to excessive diffusion channels,resulting in the oxygen diffusion into the matrix easily.However,for the near-γ and dual-phase microstructures,the atoms diffusion channels were significantly reduced,and a large number of γ grains showed excellent oxidation resistance,which significantly reduced oxygen diffusion and oxidation rates,thereby improving the high-temperature oxidation resistance of TiAl alloys.
TiAl alloySPSmicrostructurehigh temperature oxidation
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