Abstract：Gradient nanopolycrystalline structured metals are receiving increasing attention due to their unique plastic deformation mechanism and possible mechanical property enhancement. In this paper, the effect of different gradient nanostructures on the shear deformation behavior is investigated using a molecular dynamics approach. By comparing the dislocation evolution and atomic structure of grains during shear deformation of different gradient nanostructures, it is found that the deformation mechanisms of different gradient nanostructures are basically the same in the initial and intermediate stages of shear deformation process, with a large number of dislocations moving and accumulating at the grain boundaries, and then passing through the grain boundaries and finally releasing at the grain surface. In the middle and later stages of the deformation process, the different gradient nanostructures behave differently. For structures with higher shear strength, there is no shear band through multiple grains after shear deformation, and some of the coarse grains are broken into several smaller grains due to the large difference between grain orientation and shear direction and grain rotation, while the fine grains do not change significantly. The shear strength of the smaller structures is seriously affected by the shear bands formed during shear deformation due to dislocation plugging and release and interconnection of grain boundaries.
[1] 周昊飞. 梯度纳米结构金属力学性能, 变形机理和多尺度计算研究进展[J]. 固体力学学报, 2019, 40(3): 193-212. ZHOU Haofei.Progress in mechanical properties of gradient nanostructured metals, deformation mechanisms and multi-scale calculations[J]. Chinese Journal of Solid Mechanics, 2019, 40(3): 193-212. [2] LI X, LU L, LI J, et al.Mechanical properties and deformation mechanisms of gradient nanostructured metals and alloys[J]. Nature Reviews Materials, 2020, 5(9): 706-723. [3] 卢柯. 梯度纳米结构材料[J]. 金属学报, 2015, 51(1): 1-10. LU Ke.Gradient nanostructured materials[J]. Acta Metallurgica Sinica, 2015, 51: 1-10. [4] FANG T H, LI W L, TAO N R, et al.Revealing extraordinary intrinsic tensile plasticity in gradient nano-grained copper[J]. Science, 2011, 331(6024): 1587-1590. [5] LEE Z, WITKIN D B, LAVERNIA E J, et al.Bimodal structured bulk nanocrystalline Al-7.5 Mg alloy[J]. MRS Online Proceedings Library, 2003: 791-799. [6] LIU Y, LIU M, CHEN X, et al.Effect of Mg on microstructure and mechanical properties of Al-Mg alloys produced by high pressure torsion[J]. Scripta Materialia, 2019, 159: 137-141. [7] CAO H, YE X, LI H, et al.Microstructure, mechanical and tribological properties of multilayer Ti-DLC thick films on Al alloys by filtered cathodic vacuum arc technology[J]. Materials & Design, 2021, 198: 109320. [8] KULKARNI A R, SHUKLA A K, PRABU S M, et al.Investigations on enhancing the surface mechanical and tribological properties of A356 Al alloy using pulsed laser-assisted nitriding[J]. Applied Surface Science, 2021, 540: 148361. [9] LIU M, ZHENG R, LI J, et al.Achieving ultrahigh tensile strength of 1 GPa in a hierarchical nanostructured 2024 Al alloy[J]. Materials Science and Engineering A, 2020, 788: 139576. [10] LIU P, HU J Y, LI H X, et al.Effect of heat treatment on microstructure, hardness and corrosion resistance of 7075 Al alloys fabricated by SLM[J]. Journal of Manufacturing Processes, 2020, 60: 578-585. [11] 张亮, 李茂军, 司乃潮. 复合热处理对7075铝合金组织和力学性能的影响[J]. 有色金属工程, 2019, 9(9): 93-98. ZHANG Liang, LI Maojun, SI Naichao.Effect of composite heat treatment on the organization and mechanical properties of 7075 aluminum alloy[J]. Nonferrous Metals Engineering, 2019, 9(9): 93-98. [12] 张宏辉, 李旭, 项胜前, 等. 6XXX 系变形铝合金的合金化原理和生产应用[J]. 轻合金加工技术, 2012, 40(3): 12-17. ZHANG Honghui, LI Xu, XIANG Shengqian, et al.Alloying principles and production applications of 6XXX series deformed aluminum alloys[J]. Light Alloy Fabrication Technology, 2012, 40(3): 12-17. [13] OVID'KO I A, VALIEV R Z, ZHU Y T. Review on superior strength and enhanced ductility of metallic nanomaterials[J]. Progress in materials science, 2018, 94: 462-540. [14] SABIROV I, MURASHKIN M Y, VALIEV R.Nanostructured aluminium alloys produced by severe plastic deformation: New horizons in development[J]. Materials Science and Engineering A, 2013, 560: 1-24. [15] BOBRUK E V, MURASHKIN M Y, KAZYKHANOV V U, et al.Superplastic behavior at lower temperatures of high‐strength ultrafine‐grained Al alloy 7475[J]. Advanced Engineering Materials, 2019, 21(1): 1800094. [16] CHENG Z, ZHOU H, LU Q, et al. Extra strengthening and work hardening in gradient nanotwinned metals[J]. Science, 2018, 362(6414): eaau1925. [17] ZHOU K, ZHANG T, LIU B, et al.Molecular dynamics simulations of tensile deformation of gradient nano-grained copper film[J]. Computational Materials Science, 2018, 142: 389-394. [18] AURENHAMMER F.Voronoi diagrams-a survey of a fundamental geometric data structure[J]. ACM Computing Surveys (CSUR), 1991, 23(3): 345-405. [19] STUKOWSKI A.Structure identification methods for atomistic simulations of crystalline materials[J]. Modelling and Simulation in Materials Science and Engineering, 2012, 20(4): 045021. [20] PLIMPTON S.Fast parallel algorithms for short-range molecular dynamics[J]. Journal of computational physics, 1995, 117(1): 1-19. [21] JIN H S, SONG P, JON C G, et al.Thermodynamic properties of FCC metals using reparameterized MEAM potentials[J]. Indian Journal of Physics, 2021, 95(12): 2553-2565. [22] JELINEK B, GROH S, HORSTEMEYER M F, et al.Modified embedded atom method potential for Al, Si, Mg, Cu, and Fe alloys[J]. Physical Review B, 2012, 85(24): 245102. [23] STUKOWSKI A.Visualization and analysis of atomistic simulation data with OVITO-the open visualization tool[J]. Modelling and Simulation in Materials Science and Engineering, 2010, 18(1): 015012. [24] STUKOWSKI A, ALBE K.Extracting dislocations and non-dislocation crystal defects from atomistic simulation data[J]. Modelling and Simulation in Materials Science and Engineering, 2010, 18(8): 085001. [25] ZHAO J, LU X, YUAN F, et al.Multiple mechanism based constitutive modeling of gradient nanograined material[J]. International Journal of Plasticity, 2020, 125: 314-330.
2022, Vol. 27 
