625合金在750℃长时热老化时的组织演化及力学行为研究

Mechanical Behavior and Microstructure Evolution of 625 Alloy During Long-term Thermal Aging Process at 750℃

摘要:

利用扫描电镜(SEM)、透射电镜(TEM)等研究了625合金的显微组织随热老化时间的演化,并结合拉伸和硬度测试,揭示了750℃热老化1万小时过程中显微组织变化对力学性能的作用规律。结果表明,在750℃条件下,625合金中存在亚稳态γ′′相→稳态δ相的相变过程,δ相是该温度下合金的主要强化相。随热老化时间延长,γ′′相在初期迅速析出长大后不断减少直至消失,而δ相则不断增多变大,最终演变为贯穿整个晶粒的针片状相；随热老化时间延长,合金抗拉强度、屈服强度、硬度等力学性能指标不断提高,但延伸率不断降低,热老化3000 h后各项性能逐渐趋于稳定。不同形态的δ相均能对625合金起到有效的强化作用。

Abstract:

In order to clarify the performance of 625 alloy during 10000 h long term thermal aging at 750℃, the mechanical behavior and microstructure evolution were investigated by means of Scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as tensile and hardness tests. Results show that a phase transition from the metastable γ" phase to the steady-state δ phase occurs in 625 alloy at 750℃. At the initial stage γ" phase rapidly precipitates and grows in matrix, and then decreases and disappears with the extension of thermal aging. While the transformed δ phase gradually nucleates and grows in size, and turns to be the main strengthening phase in 625 alloy in the long run. With the prolonging of the thermal aging time, tensile strength, yield strength and hardness of the alloy are continuously improved, with the elongation constantly reducing. After 3000 h’s thermal aging treatment, the mechanical properties tend to keep stable. There was no significant difference between the two types of δ phase in the reinforcement of 625 alloy.