Berahmand M, Ketabchi M, Jamshidian M, Tsurekawa S
Department of Materials and Metallurgical Engineering, Amirkabir University of Technology, Tehran, 15875-4413, Iran; Division of Materials Science and Chemistry, Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, 860-8555, Japan.
Department of Materials and Metallurgical Engineering, Amirkabir University of Technology, Tehran, 15875-4413, Iran.
Micron. 2021 Apr;143:103014. doi: 10.1016/j.micron.2021.103014. Epub 2021 Jan 22.
The evolution of the microstructure and deformation mechanism at different levels of plastic strain are investigated for 304 L austenitic steel with a combination of micro X-ray diffraction (XRD), electron backscattered diffraction (EBSD) and electron channeling contrast imaging (ECCI). A plastic strain gradient is developed along the longitudinal rolling direction in a wedge-shaped 304 L austenitic steel sample. The graded deformed microstructure includes various amounts of deformation bands, ε- and α'-martensites, and their intersections form during the plastic deformation. ECCI observations reveal several deformation mechanisms of the formation of partial dislocations, dislocations, and interactions. This study suggests geometrically necessary deformation bands (GNDBs) are introduced and stored instead of geometrically necessary dislocations (GNDs) in low stacking fault energy (SFE) materials such as austenite steels. Consequently, increasing the strain gradient leads to an increase in the geometrically necessary martensitic transformation (GNMT); this is the result of the deformation-induced martensite in these materials. In addition to the statistically stored dislocations (SSDs), GNDs are generated at the grain boundaries of the fragmented grains to preserve the continuity of the grains. Accordingly, the strain hardening of the austenite steel includes multiple interactions of the deformation bands, SSDs, GNDs, GNDBs, and GNMT. From the viewpoint of microstructure design, our study provides quantitative information about the relationship between the amount of plastic deformation and the extent of microstructure evolution, in a continues design space.
采用微观X射线衍射（XRD）、电子背散射衍射（EBSD）和电子通道衬度成像（ECCI）相结合的方法，研究了304L奥氏体钢在不同塑性应变水平下的微观结构演变和变形机制。在楔形304L奥氏体钢样品中，沿纵向轧制方向形成了塑性应变梯度。梯度变形微观结构包括不同数量的变形带、ε-马氏体和α'-马氏体，它们在塑性变形过程中相互交叉形成。ECCI观察揭示了部分位错、位错和相互作用形成的几种变形机制。本研究表明，在诸如奥氏体钢等低堆垛层错能（SFE）材料中，引入并存储了几何必要变形带（GNDBs）而非几何必要位错（GNDs）。因此，增加应变梯度会导致几何必要马氏体转变（GNMT）增加；这是这些材料中变形诱导马氏体的结果。除了统计存储位错（SSDs）外，在破碎晶粒的晶界处还会产生GNDs，以保持晶粒的连续性。因此，奥氏体钢的应变硬化包括变形带、SSDs、GNDs、GNDBs和GNMT的多重相互作用。从微观结构设计的角度来看,我们的研究在连续设计空间中提供了关于塑性变形量与微观结构演变程度之间关系的定量信息。
