BSTMUF601合金高溫蠕變變形機制的實驗研究HIGH TEMPERATURE CREEP DEFORMATION MECHANISM OF BSTMUF601 SUPERALLOY

對 BSTMUF601 合金在不同溫度和應力條件下進行了拉伸蠕變實驗, 獲得了該合金的高溫蠕變的變形規(guī)律, 基于此提出了一種新的修正 θ 映射法蠕變本構模型, 該模型考慮了蠕變3階段的蠕變特點. 模型預測結果與實驗結果吻合較好, 平均相對誤差為1.86%, 相對于沒有考慮第2階段的θ映射法模型和沒有考慮第1階段的修正θ映射法模型相對誤差分別減少0.1%和6.02%, 表明該模型具有較強的適用性, 且不降低預測精度. 對蠕變和蠕變斷裂試樣的位錯組態(tài)和空洞演化進行了顯微分析, 結果表明, 穩(wěn)態(tài)蠕變階段蠕變應力指數(shù)都接近 5, 合金主要通過位錯攀移越過γ′ 相的方式變形, 并未觀察到層錯和微孿晶存在于γ′ 相或基體中, 蠕變變形機制主要是位錯攀移. 空洞在晶界上形核, 長大連接形成裂紋, 在應力集中作用下, 裂紋沿晶界擴展, 最終導致斷裂, 蠕變斷裂機制主要是晶界斷裂.
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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