Wen Yan

Bio: Wen Yan is an academic researcher from Northwestern Polytechnical University. The author has contributed to research in topics: Dislocation & Single crystal. The author has an hindex of 7, co-authored 12 publications receiving 131 citations.

Microstructure and texture evolution of cold drawing 〈110〉 single crystal copper

Abstract: By means of electron backscattering diffraction and transmission electron microscopy the microstructure and texture of drawn single crystal copper with initial orientation 〈110〉 parallel to axial direction have been investigated in the present work In order to analyze the effect of initial orientation on microstructure and texture of drawn copper, the results of the drawn 〈100〉 single crystal copper wires have been compared with 〈110〉 and 〈111〉 single crystal copper wires It is found that the grain subdivision of 〈110〉 single crystal is more evident than that of 〈100〉 and 〈111〉, and the textures consisting of 〈111〉 and 〈100〉 abruptly form in the drawn 〈110〉 single crystal At high strains, due to shear strain, the distribution of fiber textures is imhomogenous along the radial direction of drawn 〈110〉 single crystal copper wires 〈100〉 is near the surface and 〈111〉 is at the center The microstructure results of drawn 〈110〉 single crystal show that at low strains, it can be characterized as two kinds of geometrically necessary boundaries with noncrystalline character At medium strains, S bands can be observed At high strains, lamellar boundaries form Mean misorientation and average spacing of dislocation boundary are larger in drawn 〈110〉 single crystal, as compared with 〈111〉 and 〈100〉 In drawn 〈110〉 single crystal with high strains, the bimodal distribution forms at lower strains than in drawn 〈100〉 single crystal, which is because the dislocation boundaries with high angle are contributed by not only the boundary between 〈111〉 and 〈100〉 fiber textures but also the boundary in 〈111〉 or 〈100〉 texture

Fatigue cracking at twin boundaries: Effects of crystallographic orientation and stacking fault energy (vol 60, pg 3113, 2012)

Abstract: [Zhang, Z. J.; Zhang, P.; Li, L. L.; Zhang, Z. F.] Chinese Acad Sci, Shenyang Natl Lab Mat Sci, Inst Met Res, Shenyang 110016, Peoples R China.;Zhang, ZF (reprint author), Chinese Acad Sci, Shenyang Natl Lab Mat Sci, Inst Met Res, 72 Wenhua Rd, Shenyang 110016, Peoples R China.;zhfzhang@imr.ac.cn

Cell and band structures in cold-rolled polycrystalline copper

Abstract: The effect of plastic strain on the deformation microstructure has been investigated in polycrystalline copper rolled at room temperature to 5, 10, 20, and 30% reduction in thickness (equivalent strain 0·06–0·42). Results from transmission electron microscopy (TEM) observations show that dense dislocation walls (DDWs) and cells develop during the initial stages of cold rolling. Grains having a high density of DDWs are described as high wall density (HWD) structures, and grains having a low density of DDWs are described as low wall density (LWD) structures. These structures are characterised by cell size, misorientation across the cell walls, and the crystallographic orientation of the grains in which they appear. The DDWs in the HWD structures have special characteristics, extending along several cells and having a misorientation across them greater than that across ordinary cell boundaries at the same strain. The DDWs appear to have a macroscopically determined orientation. Analysis of their crys...

Electrospun hollow cage-like α-Fe2O3 microspheres: synthesis, formation mechanism, and morphology-preserved conversion to Fe nanostructures

Abstract: Hollow cage-like α-Fe2O3 microspheres with an average diameter of 500 nm and a shell thickness of 60 nm were successfully synthesized by a simple electrospinning technique using ferric nitrate (Fe(NO)3·9H2O) and polyvinylpyrrolidone (PVP) as precursors. Fe(NO)3/PVP composite microspheres were calcined at high temperature to form an interconnected 3D hollow cage-like α-Fe2O3 structure. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and magnetic measurements were used to characterize the morphology, structure, and magnetic properties of α-Fe2O3 microspheres. Based on the characterization results, a formation mechanism for electrospun hollow cage-like α-Fe2O3 microspheres was proposed. We also found that morphology-preserved conversion from α-Fe2O3 to magnetic Fe can be achieved during reduction reactions in H2/Ar. The magnetic property investigation showed that the as-prepared hollow Fe nanostructures exhibit a ferromagnetic behavior and possess high saturation magnetization (Ms).