通过分析不同微观组织TiAl合金在 850℃下的恒温氧化行为,揭示了不同微观组织TiAl合金的高温氧化机制.研究表明,近γ组织和双态组织TiAl合金表现出优异的高温抗氧化性,850℃恒温氧化 100 h后,样品表面氧化膜厚度分别为 13.78、12.81 μm,而全片层组织TiAl合金在同等条件下的氧化膜厚度为 19.06 μm.经 850℃氧化 100 h后,不同微观组织 TiAl 合金表面均形成了不具有保护作用的 TiO2/Al2O3 混合氧化层.全片层组织 TiAl 合金高温抗氧化性不足的主要原因是基体中存在过多的原子扩散通道(片层晶界和板条相界),导致大量的氧进入基体发生氧化反应,而近 γ 组织和双态组织中原子扩散通道明显减少,且存在大量抗氧化性能优异的 γ 晶粒,显著降低了氧扩散与氧化速率,从而提高了TiAl合金的高温抗氧化性能.
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.