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利用高温蠕变试验,研究SRR99单晶高温合金在低应变速率下的动态再结晶行为。结果显示,在大气环境且无涂层保护的情况下,长时间高温低应力作用会使单晶合金发生动态再结晶,动态再结晶的温度和临界应变量均低于静态再结晶,再结晶晶粒均位于试样边缘的γ′相贫化层内,再结晶深度较浅,一般不超过15μm。在高温低应变速率下,再结晶以完整晶粒的形式发生,晶粒内无条状γ′相存在。单晶合金在高温低应变速率下的动态再结晶行为主要与高温氧化有关。在实际服役条件下,表面涂层可有效抑制动态再结晶的发生。此外,还利用高温压缩试验,研究了SRR99单晶合金在高应变速率下的动态再结晶行为。在高应变速率下,单晶合金发生动态再结晶的温度和临界应变量均显著提高,再结晶以胞状组织的形式发生,晶胞内含有大量粗大的条状γ′相。
Using high temperature creep test, the dynamic recrystallization behavior of SRR99 single crystal superalloy at low strain rate was studied. The results show that under the conditions of atmospheric environment and without coating protection, the dynamic recrystallization of single crystal alloy occurs under long time high temperature and low stress. The temperature and critical strain of dynamic recrystallization are lower than those of static recrystallization The grains are all located in the γ ’phase depleted layer on the edge of the sample, and the recrystallization depth is shallower, generally not exceeding 15μm. At high temperature and low strain rate, recrystallization takes place in the form of intact grains, with the presence of a bar-free γ ’phase in the grains. The dynamic recrystallization behavior of single crystal alloys at high temperature and low strain rate is mainly related to high temperature oxidation. In actual service conditions, the surface coating can effectively inhibit the occurrence of dynamic recrystallization. In addition, the dynamic recrystallization behavior of SRR99 single crystal alloy at high strain rate was also studied by high temperature compression test. Under high strain rate, the temperature and the critical strain of single crystal alloy during recrystallization increase remarkably. Recrystallization occurs in the form of cellular structure, and the unit cell contains a large number of coarse γ ’phases.