Microstructural evolution and mechanical behavior of commercially pure Fe during severe deformation by cold caliber rolling followed by wire drawing were investigated using transmission electron microscopy and electron backscatter diffraction. Following by a drastic increment of strength in the early stage of deformation, shear banding as a softening mechanism leads to decreasing of work hardening rate and finally a steady state situation at medium strains, creating a bimodal microstructure. Increasing strain beyond 3 is associated with increasing the rate of work hardening and refinement of the material. Severely deformed Fe after cold caliber rolling to equivalent strain of 4.5 evolves from lamellar ultrafine-grained structure. Additional deformation by drawing results in more homogeneous structure and activates new mechanisms. A dynamic recovery appears at severe strains through mechanically assisted triple junction motion. It is found that suppression of triple junction motion enhances the refinement of microstructure and the strength, such that the highly deformed Fe after equivalent strain of 7 has a nano/ultrafine-grained structure combined with a high tensile strength of 1115 MPa.

中文翻译：

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严重变形的纯铁的纳米结构演化和变形机理

使用透射电子显微镜和电子背散射衍射研究了商用纯铁在冷口径冷轧随后拉丝的剧烈变形过程中的组织演变和力学行为。紧随变形初期强度的急剧增加，剪切带作为一种软化机制会导致加工硬化率降低，并最终导致中等应变下的稳态，从而形成双峰微结构。将应变增加到3以上会增加材料的加工硬化和细化的速度。冷口径轧制至等效应变为4.5后的严重变形铁从片状超细晶粒组织演变而来。通过拉伸产生的附加变形会导致结构更均匀，并激活新的机制。通过机械辅助的三结运动，在严重应变下会出现动态恢复。发现抑制三重接合运动增强了显微组织和强度的细化，使得当等效应变为7之后的高度变形的Fe具有纳米/超细晶粒结构以及1115MPa的高拉伸强度。