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采用压缩拉伸连续加载变形实验方法,即第一阶段压缩变形量0%~40%,第二阶段拉伸至断裂,研究了Mn18Cr18N奥氏体不锈钢的室温压缩拉伸变形行为.结果表明,随着压缩量的增大,后续拉伸阶段的屈服应力和均匀塑性变形最大拉伸应力、断面收缩率和延伸率均呈先增大后减小的变化规律.临界压缩量25%处,拉伸屈服应力和最大拉伸应力达到最大值,分别约为1039.97和1439.20 MPa;试样的断面收缩率和延伸率也达到最大值,分别为68.99%和73.80%.微观组织和断口形貌的OM和SEM观察结果表明,当压缩量小于临界值时,拉伸试样断口宏观形貌呈典型的杯锥状,微观形貌呈韧窝状的韧性断裂,微观组织为变形拉长的晶粒组织;当压缩量超过临界值时,拉伸试样断口宏观形貌比较平齐,微观形貌为无韧窝状的结晶状特征,微观组织为包含大量孪晶的等轴晶粒.TEM分析表明,压缩量较小时,位错通过滑移形成不同密度的位错组态;反向加载拉断后,仍能观察到位错的堆积.压缩量较大时,形成2个方向交割的孪晶;反向加载拉断后,孪晶呈平行排列,且伴有高密度位错缠结.
The compressive deformation of the Mn18Cr18N austenitic stainless steel was studied by compressive and tensile continuous loading deformation experiment, that is, compressive deformation in the first stage was 0% ~ 40% and the second stage was extended to rupture. The tensile deformation behavior of Mn18Cr18N austenitic stainless steel at room temperature was studied. With the increase of the compressive strength, the yield stress in the subsequent drawing stage and the maximum tensile stress in uniform plastic deformation, the shrinkage and elongation of the section both increase and then decrease, and the critical compression amount is 25% The maximum yield stress and the maximum tensile stress reached about 1039.97 and 1439.20 MPa, respectively, and the maximum values of the percentages of reduction and elongation of the specimens reached 68.99% and 73.80%, respectively.The OM and SEM of the microstructure and fracture morphology SEM observations show that when the compressive strength is less than the critical value, the macroscopic morphology of the tensile specimen shows a typical cup-cone shape with a ductile ductile fracture at microscopic morphology and a deformed elongated grain structure at the microstructure. When the amount of compression exceeds the critical value, the macroscopic appearance of the tensile specimen is flat and the microstructure is a non-dimpled crystalline feature, and the microstructure is equiaxed grains containing a large number of twins.TEM analysis shows that, When the amount of compression is small, the dislocation passes through the slippage The formation of dislocation configuration with different densities.After the reverse loading, the stacking of dislocations can still be observed.When the amount of compression is large, twins which are delivered in two directions are formed.The twins are arranged in parallel after the reverse loading, Accompanied by high density dislocation entanglement.