CAJ | 학술논문

利用OM,SEM和XRD对单轴非对称应力循环下304不锈钢棘轮变形过程中的微观组织变化进行了实验观察.结果表明:304不锈钢棘轮变形过程中,当棘轮应变达到一定值后会产生应变诱发马氏体相变,形成板条状马氏体,并且随循环周次的增加,形成的应变诱发马氏体相对量逐渐增加.因马氏体相变而诱发的塑性变形对总的棘轮变形量产生一定的影响,材料的棘轮应变应由两部分组成,即应力引起的塑性应变和相变诱发的塑性应变.
이용OM,SEM화XRD대단축비대칭응력순배하304불수강극륜변형과정중적미관조직변화진행료실험관찰.결과표명:304불수강극륜변형과정중,당극륜응변체도일정치후회산생응변유발마씨체상변,형성판조상마씨체,병차수순배주차적증가,형성적응변유발마씨체상대량축점증가.인마씨체상변이유발적소성변형대총적극륜변형양산생일정적영향,재료적극륜응변응유량부분조성,즉응력인기적소성응변화상변유발적소성응변.
Ratcheting behavior of the materials has been extensively investigated and simulated in the last two decades.since it is important in the design and assessment of engineering structure components subjected to asymmetrical stress-controlled cyclic loading.However.most of the referable fiterature concerned only the macroscopic phenomenon of ratcheting and its phenomenological models. Therefore.the microstructure evolution of SS304 stainless steel during uniaxial stress--controlled cyclic loading with the ratcheting deformation was observed by using OM.SEM and XRD methods.Several specimens with the same applied sttess level were first tested under the stress-controlled cyclic loading with diirerent numbers of cycles macroscopically,and then the thin-filmed samples obtained from the specimens subjected to difierent numbers of cycles were microscopically observed.The results show that when the ratcheting strain reaches a certain value high enough,the strain-induced martensite transformation Occurs in the process of ratcheting deformation.The resultant phase is the lath α-martensite and the amount of the induced martensite increases gradually with the number of cycles,which is proved by the quantitative analysis of XRD.It is also concluded that the plastic deformation caused by the martensite transformation has a un-negligible contribution to the total value of ratcheting strain.The total ratcheting deformation should be considered as a superimposition of two parts. I,e the one caused by apphed cyclic stress and the other caused by the strain-induced martensite transformation.