Pal Snehanshu, Meraj Md
Department of Metallurgical and Materials Engineering, National Institute of Technology Rourkela, Rourkela, 769008, India.
Department of Mechanical Engineering, G H Raisoni Academy of Engineering & Technology, Nagpur, 440016, India.
J Mol Model. 2019 Aug 29;25(9):282. doi: 10.1007/s00894-019-4177-2.
In this paper, simulated biaxial creep deformation behaviour for nanocrystalline (NC) nickel (Ni) has been performed at various applied load (i.e. 1 GPa, 1.4 GPa, 2 GPa, 2.5 GPa and 3 GPa) for a particular temperature (i.e. 1210 K) using molecular dynamics (MD) simulation to investigate underlying deformation mechanism based on the structural evolution during biaxial creep process. Primary, secondary and tertiary stages of creep are observed to be exhibited significantly only at 3 GPa applied stress. While, only primary and secondary stages of creep are exhibited at 1 GPa applied stress. Atomic structural evaluation, dislocation density, shear strains, atomic trajectory, inverse pole figures and grain orientation with texture distribution have been carried out to evaluate structural evolution. Stress exponent (m) for NC Ni is analysed for a particular creep temperature (i.e. 1210 K) and obtained m value is 1.30. According to shear strains counter plot, accumulation of higher shear strains are observed at grain boundary (GB) during biaxial creep deformation. It is found that dislocation density during biaxial creep is increased with the progress of creep process. Grain rotation and texture evaluation during biaxial creep process are studied using grain tracking algorithm (GTA). Grain rotation in ultrafine-grained NC Ni specimen during biaxial creep deformation is happened and exhibits almost distinct distribution, which is occurred due to the atomic shuffling within the GBs. Grain growth of ultrafine grained NC Ni is observed during biaxial creep deformation which is caused by mechanical stress.
在本文中，利用分子动力学（MD）模拟，在特定温度（即1210K）下，对纳米晶（NC）镍（Ni）在各种外加负载（即1GPa、1.4GPa、2GPa、2.5GPa和3GPa）下的双轴蠕变变形行为进行了模拟，以基于双轴蠕变过程中的结构演变来研究潜在的变形机制。仅在3GPa的外加应力下，蠕变的初级、次级和三级阶段才显著表现出来。而在1GPa的外加应力下，仅表现出蠕变的初级和次级阶段。已经进行了原子结构评估、位错密度、剪切应变、原子轨迹、反极图和具有织构分布的晶粒取向，以评估结构演变。针对特定的蠕变温度（即1210K）分析了NC Ni的应力指数（m），得到的m值为1.30。根据剪切应变反图，在双轴蠕变变形过程中，在晶界（GB）处观察到较高剪切应变的积累。研究发现，双轴蠕变过程中的位错密度随着蠕变过程的进行而增加。使用晶粒跟踪算法（GTA）研究了双轴蠕变过程中的晶粒旋转和织构评估。在双轴蠕变变形过程中，超细晶粒NC Ni试样中发生了晶粒旋转，并且呈现出几乎明显不同的分布，这是由于晶界内的原子重排所致。在双轴蠕变变形过程中观察到超细晶粒NC Ni的晶粒生长，这是由机械应力引起的。
