65Mn弹簧钢在弯曲应力下的松弛行为  

Bending Stress Relaxation Behavior of 65Mn Spring Steel

作　　者：李建明[1] 赵乃勤[1] 李群英[1] 杜希文[1] 师春生 魏芳荣[1] 

机构地区：[1]天津大学材料科学与工程学院,天津300072

出　　处：《金属热处理》2007年第5期90-94,共5页Heat Treatment of Metals

摘　　要：用自行设计制造的弹簧应力松弛连续测试系统研究了淬火回火后65Mn弹簧钢的弯曲应力松弛行为。用二阶指数衰减函数对应力松弛曲线进行了拟合,结果表明决定系数很高。用TEM对应力松弛前后试样的组织变化进行了观察,发现松弛试验前为典型的回火马氏体组织,松弛试验后出现了黑白相间的条带组织,并且观察到位错的缠结和塞积。利用热激活理论对应力松弛机理进行了研究,结果表明应力松弛过程的表观激活能随时间逐渐升高,由瞬态松弛阶段的0.24 eV升高到稳态松弛阶段的0.64 eV,由此推断应力松弛瞬态阶段主要发生位错的滑移,而在稳态松弛阶段,位错通过交滑移可以绕过碳化物质点等障碍继续运动,导致塑性应变的进一步增加。The bending stress relaxation behavior of the quenched-tempered 65Mn spring steel was investigated by a specially designed spring stress relaxation measurement system. The stress relaxation curves were fitted using the second order exponential decay function and it showed that the coefficient of determination was large. The microstructures of the specimens were examined using TEM. It could be observed that the microstructure of the specimen before stress relaxation was composed mainly of tempered martensite. A kind of microband structure was formed during stress relaxation and tangled and piled up dislocations were also observed in the relaxed specimen. The stress relaxation mechanism was analyzed using thermal activation theory and it was revealed that the apparent activation energy of the stress relaxation process increases with time from 0. 24 eV at the transient relaxation stage to about 0. 6-4 eV at the saturated relaxation stage. Thus, it could be concluded that dislocations slip during the transient stage and overcome carbide barriers in crosssliPPing in the saturated stage, this results in further increase of plastic strain.

关 键 词：弹簧钢 应力松弛 组织变化 位错机制 

分 类 号：TG142.41[一般工业技术—材料科学与工程] O377[金属学及工艺—金属材料]