预氧化对Ni_3Al合金中温塑性的影响

EFFECT OF PREOXIDATION ON DUCTILITY OF Ni_3Al BASE ALLOYS AT ELEVATED TEMPERATURE

细晶Ｎｉ－１１．８２Ａｌ－１．３Ｚｒ－０．１Ｂ合金在空气中１０００℃预氧化１５ｍｉｎ后，由于活性元素Ｚｒ的作用，氧化膜外层形成富Ｎｉ氧化膜，使空气环境下６００℃的动态脆性加剧，真空下６００℃拉伸时，预氧化处理后的细晶试样塑性仅略有降低．当预氧化环境由空气改为氩气气氛（ｐＯ２＝ｌ０－１Ｐａ）时，Ｎｉ的氧化速率约降低三个数量级Ａｌ的氧化速率片数实际上与外部施加的氧分压无关，在氩气中二者的氧化速率接近，且Ａｌ２０３较ＮｉＯ的标准生成自由能低，故在氩气环境下预氧化时形成富Ａｌ的氧化膜粗晶合金的动态脆化减弱，但在真空下６００℃拉伸时，预氧化后的粗晶试样与未经预氧化处理的试样相比。

The fine-grained Ni-11 .82Al-1 .03Zr-0. 1B alloy formed Ni-rich oxide layer after preoxidized in air at 1000℃ for 15 min. This kind of preoxidation caused a severe embrittlement at 600℃ in air, and did not affect the ductility under vacuum. When the environment of preoxidation changed from air to argon atmosphere (po2 =10-1 Pa), the oxidation rate constant decreased by a factor of 103, but the oxidation rate constant for Al is expected to be independent of the externally applied oxygen partial pressure. Free energy of the formation for Al2O3 is more negative than that for NiO. The preoxidation at the argon atmosphere , by which Al-rich oxide layer formed on the large-grain specimens, retarded the embrittlement in air, but caused a ductility loss under vacuum.