均匀化温度对K4169合金显微组织和持久性能的影响

Effect of Homogenization Temperatures on the Microstructure and Stress-Rupture Properties of K4169 Alloy

研究了两种均匀化温度下的热处理对K4169合金显微组织、Nb偏析和持久性能的影响。结果表明,随着均匀化温度的提高,合金中Laves的体积分数逐渐降低。1120℃时,Nb元素仍强烈偏析于枝晶间;当温度升高至1160℃时,Nb元素的偏析程度得到显著改善。经固溶和时效处理后,δ相分别主要以魏氏组织和颗粒状析出,1160℃处理试样中γ′′相的体积分数较大。650℃/620 MPa持久性能测试结果表明,持久寿命随均匀化温度的提高显著增加,但延伸率有所降低。持久断裂类型由穿晶韧性断裂变为沿晶-穿晶复合脆性断裂。

The influences of two homogenization temperatures on the microstructure, Nb segregation and stress-rupture properties of a K4169 alloy have been investigated. The results reveal that the amount of Laves phase decreases with the increasing of the homogenization temperature. Nb still segregates strongly in the interdendritic region after homogenization heat treatment at 1120 ℃. As the temperature raises to 1160 ℃, the microsegregation of Nb is improved distinctly. Meanwhile, Widmanstaten structure and granule-like phase are observed after solid solution and aging treatment, and a larger volume fraction of ~,＂ phase is observed in the specimen homogenized at 1160 ℃. The investigation of stress-rupture property under the condition of 650 ℃/620 MPa suggests that with the increase of the homogenization temperature, the rupture life is enhanced evidently, while the elongation decreases. Additionally, the type of fracture changes from trans-granular ductile fracture to a mixture of trans-granular and inter-granular brittle fractures.