BSTMUF601合金高温蠕变变形机制的实验研究HIGH TEMPERATURE CREEP DEFORMATION MECHANISM OF BSTMUF601 SUPERALLOY

对 BSTMUF601 合金在不同温度和应力条件下进行了拉伸蠕变实验, 获得了该合金的高温蠕变的变形规律, 基于此提出了一种新的修正 θ 映射法蠕变本构模型, 该模型考虑了蠕变3阶段的蠕变特点. 模型预测结果与实验结果吻合较好, 平均相对误差为1.86%, 相对于没有考虑第2阶段的θ映射法模型和没有考虑第1阶段的修正θ映射法模型相对误差分别减少0.1%和6.02%, 表明该模型具有较强的适用性, 且不降低预测精度. 对蠕变和蠕变断裂试样的位错组态和空洞演化进行了显微分析, 结果表明, 稳态蠕变阶段蠕变应力指数都接近 5, 合金主要通过位错攀移越过γ′ 相的方式变形, 并未观察到层错和微孪晶存在于γ′ 相或基体中, 蠕变变形机制主要是位错攀移. 空洞在晶界上形核, 长大连接形成裂纹, 在应力集中作用下, 裂纹沿晶界扩展, 最终导致断裂, 蠕变断裂机制主要是晶界断裂.
Muffle tube is the core component in a large bright annealing muffle furnace. A lot of defects will be found on the muffle tube after long-term applied under high temperature, self-weight and uneven temperature conditions, and among them creep deformation is serious, directly affecting the usability and life expectancy of muffle tube.High temperature creep and rupture properties are important indicators of the muffle tube material, and BSTMUF601 nickel-based superalloy materials are commonly used in a muffle tube. Since good oxidation resistance at high temperatures, high strength and good creep resistance, nickel-base superalloy materials are been taken seriously especially its creep mechanism.For different alloys or alloys with different conditions, the conclusions about creep mechanism are different. So the research of each alloy is necessary. Creep tests of BSTMUF601 superalloy for elevated temperature were carried out under different temperature and stress. The creep deformation characteristic of BSTMUF601 superalloy was investigated based on the creep curves. And then, a creep constitutive model for elevated temperature was proposed by introducing a modified θ projection method, which contains three stages of creep. The predicted results by using the model are in good agreement with the experimental results. The average relative error of the model fitted is1.86%.Compared with the model ignored the second stage of creep and the model ignored the first stage of creep, the average relative error was reduced 0.1% and 6.02% respectively. It is indicated that the model will be a wider range of applicationwhereasthe prediction precision is not reduced. Dislocation structure and its distribution for creep specimens and void evolution for creep rupture specimens have been carried by analyzing the microscopic structure. The results show thatthe creep stress index was close to 5during the steady-state creep stage for different temperatures. The dislocation climb mechanism controlled the creep deformation process. There was no stacking fault or microtwin observed in γ ′ phase or matrix. Cracks originate from the cavities at grain boundary and along the boundary, which led to fracture. Grain boundary fracture is the main creep rupture mechanism.
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