充氢Cr-Mo钢变形过程的声发射特征

对电化学充氢后的2.25Cr-1Mo钢进行拉伸实验,并在实时拉伸过程中采集声发射信号。结果表明:充氢后2.25Cr-1Mo钢抗拉强度为536.30MPa,下降约57MPa;断面收缩率为43.62%,下降约7%。拉伸断口上出现由氢脆引起的"白点"特征与准解理断裂形貌。充氢后试样拉伸过程弹性阶段的声发射信号活动增强,而屈服阶段的声发射信号活动减弱,变形过程的声发射信号累积绝对能量值要比未充氢试样低约1个数量级。充氢试样拉伸产生的声发射信号比未充氢试样的信号幅值降低约0.33mV,频宽降低0.06MHz。通过对声发射信号的分析发现,充氢试样变形的微观机制为氢促进位错发射与运动,而交叉滑移受到抑制。

Acoustic Emission Characteristics of Hydrogen Charged Cr-Mo Steel During Deformation

Tensile test was conducted on 2.25Cr-1Mo steel specimens that were electrochemically hy-drogen charged and acoustic emission signals were collected in the real-time stretching process.The results show that tensile strength of 2.25Cr-1Mo steel with hydrogen charging is 536.30MPa,de-creased by approximately 57MPa and reduction of area is 43.62%,decreased by 7%,compared with the specimens without hydrogen charging. Hydrogen embrittlement-induced regions known as"fisheyes"and quasi-cleavage morphology are observed on the tensile fracture surface.The AE signals activity in the elastic stage of hydrogen charged 2.25Cr-1Mo steel is enhanced,but the acoustic emis-sion signals activity in the yield stage is decreased.The cumulative absolute energy of AE signals of hydrogen charged specimens during deformation is almost one order magnitude lower than that with-out hydrogen charged specimens.The AE signals amplitude generated by the hydrogen charged speci-mens is about 0.33mV lower than that of the specimens without hydrogen charging during tensile de-formation,and that the bandwidth of signal is reduced by 0.06MHz.Though the analysis of AE sig-nals,it is found that tensile deformation microscopic mechanism of hydrogen charged specimens is that dislocation emission and motion is enhanced but dislocation cross-slip is inhibited by hydrogen.