【作者】 张弦； 龚丽； 刘静； 成林； 吴开明；

【Author】 ZHANG Xian;GONG Li;LIU Jing;CHENG Lin;WU Kai-ming;Hubei Province Key Laboratory of Systems Science in Metallurgical Process,The State Key Laboratory of Refractory Material and Metallurgy,Collaborative Innovation Center for Advanced Steels,Wuhan University of Science and Technology;

【机构】 冶金工业过程系统科学湖北省重点实验室,耐火材料与冶金省部共建国家重点实验室,高性能钢铁材料及其应用省部共建协同创新中心,武汉科技大学；

【摘要】 采用精细表征方法(SEM/EDS、TEM、XRD、EBSD),电化学测试和慢应变速率拉伸应力腐蚀试验,研究经不同预应变(0.75/1/1.25δ_s)后,在海洋环境中残余奥氏体对微纳结构贝氏体钢的应力腐蚀开裂行为的影响。结果表明,随着预应变量的增加,试验钢中残余奥氏体的含量明显下降,发生了应力诱导马氏体相变,提高了钢的屈服强度和抗拉强度。经过预应变后,一方面试验钢发生应力诱导马氏体相变,产生体积膨胀,导致应力集中,增大试验钢表面电化学活性,增加微电偶腐蚀的敏感性;另一方面试验钢位错密度增大,位错堆积的区域基体活性增强,使得试验钢表面活性位点增多,腐蚀反应增强;因此随着预应变载荷量增加,微纳结构贝氏体钢的腐蚀电流密度增大,电化学腐蚀速率增大。慢应变速率拉伸应力腐蚀试验结果表明;随着预应变载荷量增大,试验钢的应力腐蚀敏感性呈先下降后上升的趋势,当预应变载荷量为1δ_s,试验钢的应力腐蚀敏感性最低。与常规钢相比,预应变钢在拉伸过程中由相变引起的应力集中较少,阳极溶解减弱,应力腐蚀敏感性下降;随着预应变载荷量增大,试验钢的SCC裂纹萌生不仅会受到微电偶腐蚀的影响,还会受到位错堆积和残余微应力的影响,滑移带和位错堆积的基体表面活性高,更容易发生腐蚀,优先溶解形成蚀坑,成为裂纹萌生源,应力腐蚀敏感性增大。更多还原

【Abstract】 Based on characterization methods(SEM/EDS,TEM,XRD,EBSD),electrochemical test and slow strain rate tensile stress corrosion tests,the effects of retained austenite on the electrochemical and stress corrosion cracking behavior of micro/nano-structured bainitic steel were investigated in a marine environment after different pre-strains(0.75/1/1.25δ_s).The results showed that with increased pre-strain,the content of residual austenite decreased obviously,which indicated stress-induced martensitic transformation,leading to the improvement of yield strength and tensile strength of the steel.After prestrain of the test steel,on the one hand,austenite underwent deformation induced martensitic transformation,resulting in volume expansion and stress concentration,increasing the electrochemical activity of the surface of the test steel,further increasing the sensitivity to micro-galvanic corrosion;On the other hand,the dislocation density of the test steel increased,and the matrix activity in the dislocation accumulation area increased,resulting in an increase in active sites on the surface of the test steel,enhancing corrosion reactions and decreasing corrosion resistance.The slow strain rate tensile stress corrosion test results showed that with the increase of pre-strain loading,the stress corrosion sensitivity of the test steel first decreased and then increased.When the pre-strain load was 1δ_s,the test steel had the lowest the stress corrosion sensitivity.Compared with conventional steels,pre-strained steels had less stress concentration caused by phase transformation during tensile process,weakened anodic dissolution,and decreased stress corrosion sensitivity.With the increase of pre-strain loading,SCC crack initiation in the test steel was not only affected by micro-galvanic corrosion,but also affected by dislocation accumulation and residual micro-stress.The matrix with high surface activity due to the accumulation of slip bands and dislocations was more prone to corrosion,preferentially dissolving to form corrosion pits,which became the source of crack initiation and increased stress corrosion sensitivity.更多还原