【作者】 王帅； 卢子兴； 杨振宇；

【Author】 Wang Shuai;Lu Zixing;Yang Zhenyu;Institute of Solid Mechanics, School of Aeronautic Science and Engineering, Beihang University (BUAA);

【机构】 北京航空航天大学航空学院固体力学研究所；

【摘要】 孪晶界作为一种特殊的低能态共格晶界,被证明在纳米材料中能有效地阻碍位错运动,从而可以在提高纳米材料强度的同时保留良好的塑性。本文以孪晶铜纳米线为研究对象,构建多种纳米线模型,研究了孪晶界倾角、间距及梯度分布等因素对纳米线弯曲变形的影响,通过采用四点弯曲加载方式,模拟了纳米线在纯弯状态下的变形。结果表明,不同孪晶界倾角的纳米线模型初始塑性变形模式主要分为三类:纳米线表面不断发射平行的不全位错,去孪生和靠近纳米线中性层附近的位错形核。其中,不全位错扩展根据扩展方向不同又分为层错平行于孪晶界扩展和层错与孪晶界交割两种模式。随着孪晶界倾角增加,纳米线的弯曲模量也随之增大,不同间距的模型变形模式保持一致。针对孪晶界倾角为0°的纳米线,本文构建了孪晶界间距沿加载方向梯度分布的模型,研究纳米线受拉侧和受压侧孪晶界密度对弯曲变形的影响。本文研究了不同孪晶界倾角和间距对纳米线弯曲变形的影响,为寻找综合性能更优秀的纳米线提供了一定的参考。更多还原

【Abstract】 As a special low energy coherent grain boundary, twin boundary(TB) has been proved to be an effective barrier to dislocation movement in nanomaterials, which can improve the strength of nanomaterials and retain good plasticity. In this paper, twin copper nanowires are taken as the research object to construct a variety of nanowire models and study the influence of twin boundary angle, spacing and gradient distribution on the bending deformation of nanowires. Four-point bending is adopted to simulate the deformation in pure bending state. The results show that the deformation modes of nanowire models with different twin boundary angles are mainly divided into three types: partial dislocation extending at grain boundary and leading stacking faults,detwinning and dislocation nucleation within grains. According to different propagation directions, partial dislocation extending at grain boundary and producing stacking faults can be divided into two modes: fault expansion parallel to twin boundary and fault and twin boundary delivery. With the increase of twin boundary angle, the bending modulus of nanowires also increases. The deformation pattern of models with different twin boundary spacing remains consistent. For nanowires with a twinning boundary angle of 0°, a model of the gradient distribution of twinning boundary spacing along the loading direction is constructed in this paper, and the influence of twinning boundary density on bending deformation of nanowires under tension and compression is studied. The effects of twin boundary angles, spacing and gradient distribution on the bending deformation of nanowires are studied in this paper. It provides a reference for finding nanowires with better comprehensive properties.更多还原