Abstract In order to improve high-temperature mechanical properties and oxidation resistance of TiAl alloys, Ho element was added into Ti46Al4Nb1Mo alloy. The microstructure, high-temperature tensile property and oxidation behavior of Ti46Al4Nb1Mo alloy with different Ho content (0, 0.15%, 0.3%, atomic percent, hereafter in at.%) were investigated in this study. The results showed that Ho2O3 particles with square and rod-like shape formed by internal oxidation and the α2/γ lamellar spacing was refined with 0.15% Ho addition. When Ho content was 0.3%, irregular and large Al2Ho phases appeared at grain boundaries. Compared with Ti46Al4Nb1Mo alloy, the high-temperature tensile strength was improved with 0.15% Ho and decreased with 0.3% Ho. The improvement of the strength resulted from the Ho2O3 second phase strengthening, the decreasing of the strength was caused by the formation of large irregular Al2Ho phase. Oxidation testing results indicated that 0.15% Ho improved oxidation resistance of Ti46Al4Nb1Mo alloy, which was due to suppression of inward diffusion of oxygen and better adhesion between oxide film and matrix.

中文翻译：

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Ho微合金化对Ti46Al4Nb1Mo合金组织演变及高温性能的影响

摘要 为了提高TiAl合金的高温力学性能和抗氧化性能，在Ti46Al4Nb1Mo合金中加入了Ho元素。研究了不同Ho含量（0、0.15%、0.3%，原子百分比，以下以at.%表示）的Ti46Al4Nb1Mo合金的显微组织、高温拉伸性能和氧化行为。结果表明，加入0.15%的Ho后，内部氧化形成方形和棒状Ho2O3颗粒，α2/γ层状间距细化。当 Ho 含量为 0.3% 时，晶界处出现不规则的大 Al2Ho 相。与Ti46Al4Nb1Mo合金相比，0.15%的Ho提高了高温抗拉强度，0.3%的Ho降低了高温抗拉强度。Ho2O3 第二相强化导致强度的提高，强度的下降是由于形成大的不规则 Al2Ho 相造成的。氧化测试结果表明，0.15%的Ho提高了Ti46Al4Nb1Mo合金的抗氧化性，这是由于抑制了氧的向内扩散以及氧化膜与基体之间更好的附着力。