摘要
为了研究奥氏体低密度钢拉伸变形过程中组织演变和加工硬化机制,采用SEM、XRD、EBSD以及TEM对Fe-30Mn-8Al-0.8C奥氏体低密度钢变形过程中的组织进行观察和分析。试验钢通过添加质量分数为8%的铝使密度相对于纯铁下降了12%,时效处理后试验钢的组织为全奥氏体,晶界处有κ-碳化物析出。室温条件下,试验钢的屈服强度、抗拉强度和总伸长率分别为525MPa、823MPa和41.8%,强塑积达到了34.4GPa·%。通过电子万能拉伸试验机将试样分别拉伸至工程应变为2%、10%、20%(对应真应变分别为0.020、0.095、0.182)和断裂。变形过程中,位错在低应变时倾向于集中在晶界和小晶粒处。应变较大时,大晶粒内部出现较多位错。随着应变的增加,晶粒逐渐细化,小角度晶界占比呈线性增长,位错密度升高,显微硬度升高,孪晶比例降低。拉伸试样的均匀变形组织EBSD分析结果和拉伸断口处的XRD结果表明变形后的组织中未出现机械孪晶和变形诱导马氏体,这证明变形过程中没有发生TWIP和TRIP效应。通过TEM试验发现在高应变下观察到泰勒晶格和微带平面位错组织,这表明该试验钢的变形机制为微带诱发塑性。定量分析了拉伸过程中滑移带间距的演变,通过滑移带间距结合公式估算流动应力,估算值与拉伸试验数据吻合,这表明动态滑移带细化是本试验钢中主要的加工硬化机制。
In order to study the microstructure evolution and work hardening mechanism of an austenitic low-density steel during tensile deformation,SEM,XRD,EBSD and TEM were used to observe and analyze the microstructure of a Fe-30Mn-8Al-0.8Caustenitic low-density steel during deformation.The density of the experimental steel was re-duced by 12%compared to pure iron upon 8%Al addition.The microstructure of the experimental steel after aging treatment was full austenite withκ-carbide precipitating at grain boundaries.The yield strength,tensile strength and total elongation of the experimental steel at room temperature were 525 MPa,823 MPa and 41.8%,respectively.The product of strength and elongation reached 34.4GPa·%.The samples were deformed until engineering strains of 2%,10%,and 20%(corresponding to true strains of 0.020,0.095,and 0.182,respectively)and fracture.Dislo-cations tended to concentrate at grain boundaries and small grains at low strains and presented in large grains at high strains during deformation.With the increase of strain,the grains were refined gradually and the fraction of grain boundaries with low angle increased linearly.The density of dislocations and microhardness increased and twin frac-tion decreased with strain.The EBSD analyses for the uniformly deformed microstructure and XRD result for the fracture showed that no mechanical twins and deformation induced martensite presented in the deformed microstruc-ture,proving that no TWIP or TRIP effect happened during deformation.Taylor lattice and microband plane disloca-tion structure were observed at high strain by TEM,indicating a deformation mechanism of microband-induced plas-ticity for the experimental steel.The evolution of the slip band spacing during tensile deformation was quantitatively analyzed.The flow stress was estimated according to the slip band spacing and formulas.The estimated value was consistent with the tensile test data,indicating that the dynamic slip band refinement was the dominant work harden-ing mechanism of the experimental steel.
作者
沈逸平
张琪
陈光辉
袁清
薛正良
徐光
SHEN Yi-ping;ZHANG Qi;CHEN Guang-hui;YUAN Qing;XUE Zheng-liang;XU Guang(State Key Laboratory of Refractories and Metallurgy,Wuhan University of Science and Technology,Wuhan 430081,Hubei,China;Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education,Wuhan 430081,Hubei,China)
出处
《钢铁》
CAS
CSCD
北大核心
2023年第3期135-143,共9页
Iron and Steel
基金
国家自然科学基金联合基金重点资助项目(U20A20270)。
关键词
低密度钢
加工硬化
微观组织
微带诱发塑性
动态滑移带细化
low density steel
work hardening
microstructure
microband-induced plasticity
dynamic slip band re-finement
