过温服役条件下GH3625合金组织稳定性研究

Study on Microstructure Stability of GH3625 Alloy during Over-temperature Service

摘要:

采用SEM、EDS、XRD、万能拉伸试验机等手段，研究了750 ℃时效不同时间对GH3625合金管材组织及力学性能的影响。结果表明：固溶态的GH3625合金在750 ℃时效1000 h后主要析出MC、M6C、M23C6、??、?相。GH3625合金时效过程中的晶粒长大和晶界处相变行为以及Nb原子的溶质拖曳作用有密切的关系。固溶态的GH3625合金在750 ℃时效(0~1000 h范围内)后晶界宽度呈现出先增后减的趋势。GH3625合金时效前后，抗拉强度变化并不明显，屈服强度呈现出持续升高的趋势，但是合金的伸长率损失了62.55%，断裂模式从延性断裂转变为脆性断裂。

Abstract:

The influence of different aging time at 750 ℃ on microstructure and mechanical properties of GH3625 alloy tube were investigated by means of OM, SEM, EDS, Universal Testing Machine and other means in this work. The results show that the MC, M6C, M23C6, ?? and ? phase are mainly precipitated in the GH3625 alloy at 750 ℃ for 1000 h. The grain growth in the aging process of GH3625 alloy is closely related to the phase transition behavior at the grain boundary and the solute drag of Nb atoms. Due to the transformation of different types of the phase at the grain boundaries, the grain boundaries width of the GH3625 alloy with increases initially and then decreases during the long-term heat preservation at 750 ℃. Before and after aging, the change of tensile strength of the alloy is not obvious, and the yield strength of alloy shows a trend of increasing continuously. However, the elongation of the alloy has lost by 62.55%, and the fracture mode changes from ductile fracture to brittle fracture.