[110]、[112]、[111]晶向钨纳米线拉伸微结构演变
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摘要
采用嵌入原子势,使用分子动力学方法,模拟研究了[110]、[112]和[111]三个晶向钨纳米线的拉伸弛豫过程的微观破坏机理.并引入共近邻分析方法、配位数及中心对称参数法来分析它的结构和形状的演化过程.结果表明:不同晶向的纳米线拉伸时具有不同的力学性能,[111]晶向具有最大的弹性模量、屈服应变、屈服强度与断裂应变,其次是[110]晶向,最后是[112]晶向.晶向对弹性模量的影响较小,但对屈服应变、屈服强度、断裂应变影响较大.模拟结果还表明:这三个晶向均具有弹性、损伤、屈服及颈缩断裂四个阶段,且发现[112]晶向具有强化阶段,即应力随应变的增加而增加,重新恢复承载能力,但其断裂应变最小.并给出了这三种不同晶向拉伸断裂的机理.
Mechanical properties and micro-structure fracture mechanism of tungsten nanowires with-crystal orientations of[110],[112]and[111]have been investigated with molecular dynamics and embedded atom methods.Simultaneously common neighbor analysis,center symmetry parameters and coordination number have been employed to analysis the evolution of structure.It is concluded that different crystal orientation nanowires have different characters.The elastic modulus,yield strain,yield-strength and the fracture stress is decrease in the sequence of[111],[110]and[112]crystal orientations.It also reveals that all of the stress-strain curves are classified into four stages:elastic stage,damage stage,yielding stage and failure stage.It concluded that crystal orientation has slightly impact on the elastic modulus but has great effect on the tensile strength,yield strength and ductility.Interest--ingly,hardening stage has been found in tungsten nanowire with crystal orientation of[112]at yielding stage.That is to say,the strain increases with the increase of stress in the hardening stage,the nanowi--re with crystal orientation of[112]has the trend that recovers its capability in strength,but consequently results in the least ductility.In the end the tensile failure mechanisms of the three nanowires have been summarized.
Mechanical properties and micro-structure fracture mechanism of tungsten nanowires with-crystal orientations of[110],[112]and[111]have been investigated with molecular dynamics and embedded atom methods.Simultaneously common neighbor analysis,center symmetry parameters and coordination number have been employed to analysis the evolution of structure.It is concluded that different crystal orientation nanowires have different characters.The elastic modulus,yield strain,yield-strength and the fracture stress is decrease in the sequence of[111],[110]and[112]crystal orientations.It also reveals that all of the stress-strain curves are classified into four stages:elastic stage,damage stage,yielding stage and failure stage.It concluded that crystal orientation has slightly impact on the elastic modulus but has great effect on the tensile strength,yield strength and ductility.Interest--ingly,hardening stage has been found in tungsten nanowire with crystal orientation of[112]at yielding stage.That is to say,the strain increases with the increase of stress in the hardening stage,the nanowi--re with crystal orientation of[112]has the trend that recovers its capability in strength,but consequently results in the least ductility.In the end the tensile failure mechanisms of the three nanowires have been summarized.
引文
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[2]Gilmer G H,Huang H,Roland C.the film deposition:fundamentals and modeling[J].Comput Mater Sci,1998,12:354.
[3]Seifert W,Carlsson N,Miller M,et al.in-situ growth of quantum dot structures by the StranskiKrastanow growth mode[J].Prog Crys Growth Charact Mater,1996,33:423.
[4]Sarlar J,Khan G G,Basumallick A.Nanowires:properties,applications and synthesis via porous anodic aluminium oxide template[J].Bull Mater Sci,2007,30:271.
[5]Craihead H G.Nanoelectromechanical systems[J].Science,2000,290:1532.
[6]韩志萍,袁林,单德彬等.纳米尺度拉伸变形行为的分子动力学模拟[J].哈尔滨工业大学学报,2006,38(10):1677.
[7]Koh S J A,Lee H P,Lu C.Molecular dynamics simulation of a solid platinum nanowire under uniaxial tensile strain:Temperature and strain-rate effects[J].Phys Rev B,2005,72:085414.
[8]Wen Y H,Zhu Z Z,Zhu R Z.Molecular dynamics study of the mechanical behavior of nickel nanowire:Strain rate effects[J].Comput Mater Sci,2008,41(4):553.
[9]徐洲,王秀喜,梁海弋.纳米丝的应变率和尺寸效应的分子学模拟[J].材料研究学报,2003,17(3):262.
[10]文玉华,周富信,刘日武等.纳米晶铜单向拉伸变形的分子动力学模拟[J].力学学报,2002,34(1):29.
[11]鲁红权,张俊乾,范镜泓.不同晶向金属纳米线拉伸力学性能的分子动力学研究[J].固体力学学报,2011,32(5):433.
[12]Cao A,Wei Y G,Mao S X.Alternating starvation of dislocations during plastic yielding in metallic nanowires[J].Scr Mater,2008,59(2):219.
[13]Cao A,Wei Y G.Atomistic simulation of the mechanical behavior of fivefold twinned nanowires[J].Phys Rev B,2006,74(21):214108.
[14]Cao A,Ma E.Sample shape and temperature strongly influence the stregth of metallic nanopillars[J].Acta Mater,2008,56(17):4816.
[15]马彬,饶秋华,贺跃辉等.单晶钨纳米线拉伸变形机理的分子动力学研究[J].物理学报,2013,56(17):176103.
[16]Ma B,Rao Q H,He Y H.Effect of crystal orientation on tensile mechanical properties of single-crystal tungsten nanowire[J].Trans Nonferrous Met Soc China,2014,24:2904.
[17]Finnis M W,Sinclair J E.A simple empirical N-body potential for transition metals[J].Philos Mag A,1984,50:45.
[18]Ackland G.J,Vitek V.Many-body potentials and atomic-scale relaxations in noble-metal alloys[J].Phys Rev B,1990,41:10324.
[19]卢敏,许卫兵,侯春菊等.银纳米杆高温熔化断裂弛豫性能的原子级模拟研究[J].物理学报,2010,59:6377.
[20]卢敏,黄惠莲,余冬海等.不同晶面银纳米晶高温熔化的各向异性[J].物理学报,2015,64:106102.
[21]Zhou X W,Johnson R A,Wadley H N G.Misfitenergy-increasing dislocations in vapor-deposited CoFe/NiFe multilayers[J].Phys Rev B,2004,69:1.
[22]Allen M P,Tildenley D J.Computer simulation of liquids[M].Oxford:Clarendon Press,1987.
[23]黄丹,陶伟明,郭乙木.镍单晶纳米丝单向拉伸的分子动力学模拟[J].兵器材料科学与工程,2005,28(3):1.
[24]Honeycutt J D,Andersen H C.Molecular dynamics study of melting and freezing of small Lennard-Jones clusters[J].J Phys Chem,1987,91:4950.
[25]Kelchner C L,Plimpton S J,Hamilton J C.Dislocation nucleation and defect structure during surface indentation[J].Phys Rev B,1998,58:11085.
[26]Huang H,Wu Y Q,Wang S L,et al.Mechanical properties of single crystal tungsten microwhiskers characterized by nanoindentation[J].Mater Sci Eng A,2009,523:193.
[27]Komanduri R,Chandrasekaran N,Raff L M.Molecular dynamics simulation of uniaxial tension of some single-crystal cubic metals at nanolevel[J].Int J Mech Sci,2001,43:2237.