拉伸与疲劳载荷下α-Ti中裂纹扩展机制的原子模拟
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摘要
采用分子动力学方法模拟研究含3种不同裂纹取向的α-Ti在拉伸载荷和疲劳载荷作用下裂纹扩展的微观机制.研究表明:B(0001)[1-210]裂纹构型通过产生变形孪晶的方式来实现垂直于基面方向的变形,单向拉伸过程中裂尖处有无位错区出现;A(1-210)[10-10]和C(1-210)[0001]裂纹构型的失效过程表明基面位错比柱面位错更容易发射;C裂纹构型循环加载时基面滑移系优先开动,使位错快速发射而释放了裂尖应力,导致裂纹出现止裂现象;含微裂纹α-Ti材料的失效过程是位错形核与发射、缺陷扩展、孪晶变形等共同作用的结果.
In this paper,molecular dynamics simulation was performed to study the failure mechanism of theα-Ti with centered pre-crack defect under uniaxial tensile and fatigue loading.Three typical pre-cracks with A(1-210)[10-10],B(0001)[1-210]and C(1-210)[0001]were chosen to simulate the effects of crack orientation on crack growth under these two loading.The deformation twinning was found in crack B,at the same time the dislocation-free zone around the crack tip was found under tensile loads.The results also indicated that dislocation emission in the base plane was easier than that in the cylindrical plane,so the crack growth of orientation C stopped because the dislocation emits rapidly along its base plane releasing the crack tip stress under the fatigue loading.The results showed that the failure mechanism ofα-Ti with crack defect was a very complicated process with many interacting factors mixed together,such as dislocation emission,carck growth,deformation twin,and so on.
In this paper,molecular dynamics simulation was performed to study the failure mechanism of theα-Ti with centered pre-crack defect under uniaxial tensile and fatigue loading.Three typical pre-cracks with A(1-210)[10-10],B(0001)[1-210]and C(1-210)[0001]were chosen to simulate the effects of crack orientation on crack growth under these two loading.The deformation twinning was found in crack B,at the same time the dislocation-free zone around the crack tip was found under tensile loads.The results also indicated that dislocation emission in the base plane was easier than that in the cylindrical plane,so the crack growth of orientation C stopped because the dislocation emits rapidly along its base plane releasing the crack tip stress under the fatigue loading.The results showed that the failure mechanism ofα-Ti with crack defect was a very complicated process with many interacting factors mixed together,such as dislocation emission,carck growth,deformation twin,and so on.
引文
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[2]ARGON A S,YIP S.Molecular dynamics simulation of crack tip processes in alpha-iron and copper[J].Journal of Applied Physics,1983,54(9):4864-4878.
[3]DIENES G J,PASKIN A.Molecular dynamic simulations of crack propagation[J].Journal of Physics and Chemistry of Solids,1987,48(11):1015-1033.
[4]ZHANG Y W,WANG T C,TANG Q H.Simulation of nucleation and emission of dislocations by molecular dynamics method[J].Journal of Applied Physics,1995,77(6):2393-2399.
[5]KUCHEROV L,TADMOR E B.Twin nucleation mechanisms at a crack tip in an hcp material:molecular simulation[J].Acta Materialia,2007,55(6):2065-2074.
[6]QI H G,GUO Y F,TANG X Z,et al.Atomistic simulation of the structural evolution in magnesium single crystal under c-axis tension[J].Acta Metall Sin,2011,24(6):487-494.
[7]YUAN Y Q,CHEN H Y,ZENG X G,et al.MD simulation on evolution of micro structure and failure mechanism around interactional voids in pure Al[J].Applied Mechanics and Materials,2014,444/445:183-190.
[8]CHANG W J,FANG T H.Influence of temperature on tensile and fatigue behavior of nanoscale copper using molecular dynamics simulation[J].Journal of Physics and Chemistry of Solids,2003,64(8):1279-1283.
[9]POTIRNICHE G P,HORSTEMEYER M F,JELINEK B,et al.Fatigue damage in nickel and copper single crystals at nanoscale[J].International journal of Fatigue,2005,27(10):1179-1185.
[10]TANG T,KIM S,JORDON J B,et al.Atomistic simulations of fatigue crack growth and the associated fatigue crack tip stress evolution in magnesium single crystals[J].Computational Materials Science,2011,50(10):2977-2986.
[11]李梁,孙健科,孟祥军.钛合金的应用现状及发展前景[J].钛工业进展,2005,21(5):19-24.
[12]PLIMPTON S J.Fast parallel algorithms for short-range molecular dynamics[J].Journal of Computational Physics,1995,117:1-19.
[13]HENNIG R G,LENOSKY T J,TRINKLE D R,et al.Classical potential describes martensitic phase transformations between theα,β,andωtitanium phases[J].Physical Review B,2008,78(5):054121.
[14]BALASUBRAMANIAN S,ANAND L.Plasticity of initially textured hexagonal polycrystals at high homologous temperatures:application to titanium[J].Acta Materialia,2002,50(1):133-148.
[15]CHICHILI D R,MESH K T,HEMKER K J.The high-strain-rate response of alpha-titanium:experiments deformation mechanisms and modeling[J].Acta Materialia,1998,46(3):1025-1043.
[16]IGARASHI M,KHANTHA M,VITEK V.N-body interatomic potentials for hexagonal close-packed metals[J].Philosophical Magazine B,1991,63(3):603-627.
[17]SIMMONS G,WANG H.Single crystal elastic constants and calculated aggregate properties[M].Cambridge:MIT Press,1971.
[18]HONEYCUTT J D,ANDERSEN H C.Molecular dynamics study of melting and freezing of small LennardJones clusters[J].Journal of Physical Chemistry,1987,91(19):4950-4963.
[19]YUAN Y Q,ZENG X G,CHEN H Y,et al.Molecular dynamics simulation on microstructure evolution during solidification of copper nanoparticles[J].Journal of the Korean Physical Society,2013,62:1645-1651.
[20]KELCHNER C L,PLIMPTON S J,HAMILTON J C.Dislocation nucleation and defect structure during surface indentation[J].Physical Review B,1998,58(17):11085-11088.