The evolution of phase composition and thermal oxidation behavior of high-entropy AlCrFeCoNiMn_x alloys (x = 0.5 and 1) during long-term oxidation at 900°C were studied. A single- phase ordered (B2) bcc alloy formed in the starting as-cast state regardless of manganese content. The scale phase composition varied with exposure time and manganese content. After 10 h of oxidation, high-entropy spinel-type MeMn₂O₄, as well as Mn₃O₄ and Al₂O₃, formed on the AlCrFeCoNiMn alloy, while only Mn₃O₄ and Al₂O₃ oxides emerged on the AlCrFeCoNiMn_0.5 alloy. Increase in the oxidation time for the equiatomic alloy up to 25 h led to spinel NiMn₂O₄ and bixbyite FeMnO₃ in the oxide scale; Mn₃O₄ and Al₂O₃ were also present. The phase composition of the oxidized layer on the AlCrFeCoNiMn_0.5 alloy did not change. After 50 h, the structure of the oxide scale was similar for both alloys and consisted of NiMn₂O₄, FeMnO₃, Mn₃O₄, and Al₂O₃ in different ratios. The oxidation kinetics of the alloys naturally depended on the manganese content: the higher the manganese content, the higher the oxidation rate. A continuous layer of the fcc solid solution rich in chromium, iron, and cobalt was observed under the scale in both alloys. An internal oxidation area was also found in the subscale layer of the AlCrFeCoNiMn alloy. Long-term (more than 50 h) oxidation at 900°C substantially changed the phase composition of the alloy matrices: the bcc (B2) solid solution underwent spinodal decomposition to form bcc and fcc phases and tetragonal σ phase. Analyses of the alloy matrices showed a sharp increase in their microhardness after annealing. This can be attributed to the formation of a significant amount of the σ phase.

研究了高熵AlCrFeCoNiMn _x合金（x = 0.5 和1）在900℃长期氧化过程中的物相组成和热氧化行为的演变。无论锰含量如何，单相有序 (B2) bcc 合金均在初始铸态下形成。氧化皮相组成随暴露时间和锰含量而变化。氧化10 h后，AlCrFeCoNiMn合金上形成高熵尖晶石型MeMn ₂ O ₄、Mn ₃ O ₄和Al ₂ O ₃，而AlCrFeCoNiMn合金上仅出现Mn ₃ O ₄和Al ₂ O ₃氧化物。 AlCrFeCoNiMn _0.5合金。将等原子合金的氧化时间延长至25小时，导致氧化皮中出现尖晶石NiMn ₂ O ₄和方铁锰矿FeMnO _{3 ；}还存在Mn ₃ O ₄和Al ₂ O _{3 。}AlCrFeCoNiMn _0.5合金氧化层的相组成没有变化。50小时后，两种合金的氧化皮结构相似，由不同比例的NiMn ₂ O ₄、FeMnO ₃、Mn ₃ O ₄和Al ₂ O ₃组成。合金的氧化动力学自然取决于锰含量：锰含量越高，氧化速率越高。在两种合金的氧化皮下均观察到富含铬、铁和钴的连续的面心立方固溶体层。在 AlCrFeCoNiMn 合金的氧化皮层中还发现了内部氧化区域。900℃下的长期（超过50小时）氧化显着改变了合金基体的相组成：bcc（B2）固溶体发生旋节线分解，形成bcc和fcc相以及四方σ相。对合金基体的分析表明，退火后其显微硬度急剧增加。这可以归因于大量σ相的形成。