变形对亚稳态奥氏体不锈钢低温敏化的影响

The effect of deformation on low temperature sensitized metastable austenite stainless steel

采用扫描电镜(SEM)、X射线衍射分析(XRD)及透射电镜(TEM)研究了不同形变量下的亚稳态不锈钢(AISI 304)经过低温敏化处理(380℃、240h的真空热处理)后组织的变化。通过双循环电化学动电位活化技术(DL-EPR)对敏化态的试样进行敏化度(DOS)测试,并用电化学阻抗谱表征了不同试样的耐腐蚀性能。结果表明,随着变形量的增加,低温敏化试样的敏化度递增,材料的耐腐蚀性能下降,当变形量达到40%时,敏化度达到71%。经过DLEPR测试后,试样奥氏体晶粒和大部分晶界完好,马氏体区域是主要腐蚀区域,腐蚀模式为穿晶腐蚀。马氏体板条和基体中的滑移带是碳化物容易形核的位置。

The microstructure of metastable austenite stainless steel （AISI 304） at different deforma- tion level after low temperature sensitization （vacuum treatment at 380 ℃ for 240 h ） were investigated by scanning electron microscope （SEM）, X-ray diffraction （XRD） and transmission electron microscopy （TEM）. Double loop electrochemical potentiokinetic reactivation （DL-EPR） method was used to test the samples＇ degree of sensitization （DOS）. And the corrosion resistance of these samples was characterized by electrochemical impedance spectroscopy （EIS）. The results indicated that the DOS value increases with the increasing deformation level as well as the corrosion resistance of the samples decreases. The DOS value of samples with 40% deformation level can reach to 71%. The morphology of the specimen surface after the measurement of DL-EPR showed that the martensite region was corroded obviously while the austenite region was corroded slightly. Transgranular corrosion happened at this condition. The carbides were easily nucleated at the martensite lath and the slip band in the matrix.