时效时间对T91钢显微组织和力学性能的影响

采用光学显微镜、扫描电镜、室温拉伸和硬度试验等研究了T91钢管在680℃时效不同时间(0、240、480、720、1200、1680和2160 h)后的显微组织和力学性能。结果表明，T91钢管在680℃时效前后的显微组织均为回火马氏体，随着时效时间的增加，显微组织的晶界越来越明显，晶粒逐渐变粗。随着时效时间的增加，T91钢的硬度缓慢降低，强度(下屈服和抗拉强度)出现先降低、再升高、后又降低、最后呈缓慢降低趋势，塑性(伸长率)出现先增加、后降低、最后缓慢降低的过程，拉伸断口由微孔聚集型断裂转变为准解理断裂。

Effect of aging time on microstructure and mechanical properties of T91 steel

Microstructure and mechanical properties of T91 steel tube after aging at 680 ℃ for 240, 480, 720, 1200, 1680 and 2160 h were studied by means of optical microscopy, scanning electron microscopy, room temperature tensile testing and hardness testing. The results show that the microstructure of the T91 steel is tempered martensite before and after aging at 680 ℃ for different time, the grain boundaries of microstructure become more and more obvious with the increase of aging time, and the grains become coarser gradually. With the increase of aging time, the hardness of the T91 steel decreases slowly, the lower yield strength and tensile strength decrease first, then increase, then decrease and finally decrease slowly, and the elongation increases first, then decreases and finally decreases slowly. The tensile fracture of the T91 steel changes from microporous fracture to quasi cleavage fracture.