12%Cr转子钢高温应变疲劳及微观组织研究

在对12%Cr转子钢在室温、566℃和600℃时进行应力-应变试验时,当滞后环曲线基本稳定后,分别选择不同循环周次卸载下未断的试样,然后重新安装一个试样在同一应力-应变曲线下进行再次试验,直到有试样失效为止.采用应变控制,应变幅分别为0.7%和1.4%,应变速率为0.004/s.用透射电镜对不同循环周次的试样进行观察,在600℃以及室温下都可观察到循环硬化现象,透射电镜研究表明,在室温和高温条件下都有位错胞出现,随着温度的增加动态回复的影响变得非常明显,高温下位错的密度明显降低,其中的位错胞经过600℃1 h回火仍然清晰可见.

Cyclic Deformation Behavior and Microstructural Changes of 12%Cr Martensitic Stainless Steel at Elevated Temperature

Strain -controlled uniaxial push- pull low- cycle fatigue testes were performed on 12% Cr mar- tensitic stainless steel at room temperature,566 ℃ and 600 ℃. Specimens were tested at total strain ampli- tudes of 1.4% and 0.7% with a constant strain rate of 0. 004/s. The microstructures of the specimens sub- jected to different cycles were studied using transmission electron microscope. Cyclic softening was observed at room temperature of 600 ℃. TEM investigations revealed that cellular structures of dislocations were formed in the fatigued specimens at both room and elevated temperatures. Dynamic recovery has a very sig- nificant effect on the dislocation structure of specimens tested at elevated temperature. The thickness and density of the dislocation cell wails formed in specimens cycled at 600 ℃ are less than that at room tempera- ture. Cellular dislocation structures formed during cycling are annihilated in the specimens subjected to one hour annealing at 600 ℃.