Metals and Materials International ( IF 3.3 ) Pub Date : 2021-09-12 , DOI: 10.1007/s12540-021-01041-3 Yuming Qi 1 , Tengwu He 1 , Miaolin Feng 1
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Abstract
Adding nanotwins to a metal could be a way to effectively improve its strength without suppressing its tensile ductility, which suggests that their unique nanostructure may alter microstructure evolution and deformation mechanisms. In this work, we perform a molecular dynamics-based tension simulation of two-dimension (2D) polycrystalline copper (Cu) with embedded nanotwins under uniaxial stress conditions. The results of MD-simulation reveal that the spacing of the twin boundaries had a significant effect on the mechanical properties of nanotwinned materials. Specifically, an irregular relationship is found between the twin boundary spacing (\(D_{T}\)) and the strength of the material. It exhibits that the peak stress reached a maximum at \(D_{T}\) = 12.5 nm and decreased thereafter with increasing average \(D_{T}\). However, flow stress reaches a maximum at a critical value of \(D_{T}\) = 7 nm. According to the analysis of microstructure evolution, the presence of nanotwins hinder the motion of partial dislocations and stacking faults, and the stress-concentrated region leads to the transition from coherent twin boundaries to incoherency. The stress-concentrated region locates in the step of incoherent would release the intrinsic stacking faults responsible for the formation of hierarchical contraction nanotwins stacking faults which efficiently improves the strength of Cu. In addition, as the tension proceeds, some samples begin to display the secondary twinning. This work will be helpful for further investigation the nucleation and evolution of 2D nanotwinned metals and for formulating effective strength criteria for 2D nanotwinned metals.
Graphic Abstract
中文翻译：
基于分子动力学的单轴应力条件下二维纳米孪晶铜塑性变形的拉伸模拟：位错和二次孪晶的演化
摘要
在金属中添加纳米孪晶可能是一种有效提高其强度而不抑制其拉伸延展性的方法，这表明它们独特的纳米结构可能会改变微观结构的演变和变形机制。在这项工作中，我们在单轴应力条件下对嵌入纳米孪晶的二维 (2D) 多晶铜 (Cu) 进行了基于分子动力学的张力模拟。MD模拟结果表明，孪晶边界的间距对纳米孪晶材料的力学性能有显着影响。具体而言，发现孪晶边界间距 ( \(D_{T}\) ) 与材料强度之间存在不规则关系。它表明峰值应力在\(D_{T}\)处达到最大值 = 12.5 nm，此后随着平均\(D_{T}\) 的增加而减小。然而，流动应力在临界值\(D_{T}\)处达到最大值 = 7 纳米。根据微观结构演化分析，纳米孪晶的存在阻碍了部分位错和堆垛层错的运动，应力集中区域导致相干孪晶边界向非相干转变。位于非相干步骤的应力集中区域将释放负责形成分层收缩纳米孪晶堆垛层错的固有堆垛层错，从而有效地提高了铜的强度。此外，随着张力的进行，一些样品开始显示二次孪晶。这项工作将有助于进一步研究二维纳米孪晶金属的成核和演化，并有助于制定二维纳米孪晶金属的有效强度标准。
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