Yang Yang, Ding Xiangdong, Sun Jun, Salje Ekhard K H
State Key Laboratory for Mechanical Behaviour of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK.
Nanomaterials (Basel). 2021 Jun 18;11(6):1602. doi: 10.3390/nano11061602.
The torsion of pristine α-Fe nanowires was studied by molecular dynamics simulations. Torsion-induced plastic deformation in pristine nanowires is divided into two regimes. Under weak torsion, plastic deformation leads to dislocation nucleation and propagation. Twisting-induced dislocations are mainly 12<111> screw dislocations in a <112>-oriented nanowire. The nucleation and propagation of these dislocations were found to form avalanches which generate the emission of energy jerks. Their probability distribution function (PDF) showed power laws with mixing between different energy exponents. The mixing stemmed from simultaneous axial and radial dislocation movements. The power-law distribution indicated strongly correlated 'wild' dislocation dynamics. At the end of this regime, the dislocation pattern was frozen, and further twisting of the nanowire did not change the dislocation pattern. Instead, it induced local amorphization at the grip points at the ends of the sample. This "melting" generated highly dampened, mild avalanches. We compared the deformation mechanisms of twinned and pristine α-Fe nanowires under torsion.
通过分子动力学模拟研究了原始α-Fe纳米线的扭转。原始纳米线中扭转诱导的塑性变形分为两个阶段。在弱扭转下，塑性变形导致位错形核和扩展。在<112>取向的纳米线中，扭转诱导的位错主要是12<111>螺型位错。发现这些位错的形核和扩展形成雪崩，产生能量猝发。它们的概率分布函数（PDF）显示出具有不同能量指数混合的幂律。这种混合源于轴向和径向位错的同时运动。幂律分布表明位错动力学存在强相关的“狂野”行为。在这个阶段结束时，位错模式被冻结，纳米线的进一步扭转不会改变位错模式。相反，它在样品末端的夹持点处诱导局部非晶化。这种“熔化”产生高度衰减的轻微雪崩。我们比较了孪晶和原始α-Fe纳米线在扭转下的变形机制。
