Alcalá Jorge, Očenášek Jan, Varillas Javier, A El-Awady Jaafar, Wheeler Jeffrey M, Michler Johann
Department of Materials Science and Metallurgical Engineering, InSup, ETSEIB, Universitat Politècnica de Catalunya, 08028, Barcelona, Spain.
New Technologies Research Centre, University of West Bohemia in Pilsen, 30614, Plzeň, Czech Republic.
Sci Rep. 2020 Nov 4;10(1):19024. doi: 10.1038/s41598-020-75934-5.
Plastic deformation in crystalline materials consists of an ensemble of collective dislocation glide processes, which lead to strain burst emissions in micro-scale samples. To unravel the combined role of crystalline structure, sample size and temperature on these processes, we performed a comprehensive set of strict displacement-controlled micropillar compression experiments in conjunction with large-scale molecular dynamics and physics-based discrete dislocation dynamics simulations. The results indicate that plastic strain bursts consist of numerous individual dislocation glide events, which span over minuscule time intervals. The size distributions of these events exhibit a gradual transition from an incipient power-law slip regime (spanning [Formula: see text] 2.5 decades of slip sizes) to a large avalanche domain (spanning [Formula: see text] 4 decades of emission probability) at a cut-off slip magnitude [Formula: see text]. This cut-off slip provides a statistical measure to the characteristic mean dislocation swept distance, which allows for the scaling of the avalanche distributions vis-à-vis the archetypal dislocation mechanisms in face-centered cubic (FCC) and body-centered cubic (BCC) metals. Our statistical findings provide a new pathway to characterizing metal plasticity and towards comprehension of the sample size effects that limit the mechanical reliability in small-scale structures.
晶体材料中的塑性变形由一系列集体位错滑移过程组成，这些过程会导致微观尺度样品中的应变突发发射。为了阐明晶体结构、样品尺寸和温度对这些过程的综合作用，我们结合大规模分子动力学和基于物理的离散位错动力学模拟，进行了一套全面的严格位移控制微柱压缩实验。结果表明，塑性应变突发由许多单个位错滑移事件组成，这些事件跨越极短的时间间隔。这些事件的尺寸分布在截止滑移量[公式：见正文]处呈现出从初始幂律滑移 regime（跨越[公式：见正文]2.5 个滑移尺寸 decade）到大型雪崩域（跨越[公式：见正文]4 个发射概率 decade）的逐渐转变。这个截止滑移为特征平均位错扫过距离提供了一种统计度量，这使得雪崩分布能够相对于面心立方（FCC）和体心立方（BCC）金属中的典型位错机制进行缩放。我们的统计结果为表征金属塑性以及理解限制小尺度结构机械可靠性的样品尺寸效应提供了一条新途径。
