Remarkable diversity is observed in dislocation interactions that are responsible for intermittent and sudden crystal slips.While large crystal slips can be easily observed on the surface of deformed crystals,unraveli...Remarkable diversity is observed in dislocation interactions that are responsible for intermittent and sudden crystal slips.While large crystal slips can be easily observed on the surface of deformed crystals,unraveling the underlying dislocation interaction mechanisms,however,has been a longstanding challenge in the study of single-crystal plasticity.A recent study demonstrated that the sluggish dislocation dynamics in the high entropy alloy(HEA)of Al_(0.1)CoCrFeNi enables the observation of slip bands for a direct link to dislocation avalanches in a nanopillar.Here,we further examined the dislocation structure of slip bands in the HEA nanopillars oriented for single slip.Experimental evidence was provided on the dislocation organization in a slip band based on groups of primary dislocations,secondary dislocations,and dislocation pileups.The results were compared with the previously proposed slip band models.The unique aspects of the HEA that enable such observations were also investigated through an examination of the dislocation microstructure and its response to applied forces in the HEA nanopillars.展开更多
Persistent slip band(PSB) is an important and typical microstructure generated during fatigue crack initiation. Intensive work has been done to investigate the mechanisms of the formation of persistent slip bands sinc...Persistent slip band(PSB) is an important and typical microstructure generated during fatigue crack initiation. Intensive work has been done to investigate the mechanisms of the formation of persistent slip bands since the 1950 s when Wadsworth[1]observed the fatigue fracture in copper. Simulations have indicated that PSBs formation during fatigue crack initiation is related to the dislocation driving force and interaction. In this paper, a molecular dynamics(MD) simulation associated with embedded atom model(EAM) is applied to the PSBs formation in nickel-base superalloys with different microstructure and temperature under tensiletensile loadings. Five MD models with different microstructure(pure γ phase and γ/γ phase), grain orientation([1 0 0][0 1 0][0 0 1]and [1 1 1][ 0 1][2 1]) and simulation temperature(300 K, 600 K, 900 K) were built up in these simulations. Our results indicated that within the γ phase by massive dislocations, pile-up and propagation which can penetrate the grain. Also, it is found that the temperature will affect the material fatigue performance and blur PSBs appearance. The simulation results are in strong agreement with published experimental test result. This simulation is based on the work^([2]). The highlights of the article include: 1) investigation of the PSB formation via molecular dynamics simulation with three different parameters, 2) conduct of a new deformation and velocity combination controlled simulation for the PSB formation, 3) high-performance computing of PSB formation, and 4) systematic analysis of the PSB formation at the atomic scale in which the dislocation plays a critical role.展开更多
基金supported by the U.S.National Science Foundation(No.DMR-1410596 to J.M.Z)supported by the centre for High-resolution Electron Microscopy(ChEM)of SPST at Shanghai Tech University(No.EM02161943)。
文摘Remarkable diversity is observed in dislocation interactions that are responsible for intermittent and sudden crystal slips.While large crystal slips can be easily observed on the surface of deformed crystals,unraveling the underlying dislocation interaction mechanisms,however,has been a longstanding challenge in the study of single-crystal plasticity.A recent study demonstrated that the sluggish dislocation dynamics in the high entropy alloy(HEA)of Al_(0.1)CoCrFeNi enables the observation of slip bands for a direct link to dislocation avalanches in a nanopillar.Here,we further examined the dislocation structure of slip bands in the HEA nanopillars oriented for single slip.Experimental evidence was provided on the dislocation organization in a slip band based on groups of primary dislocations,secondary dislocations,and dislocation pileups.The results were compared with the previously proposed slip band models.The unique aspects of the HEA that enable such observations were also investigated through an examination of the dislocation microstructure and its response to applied forces in the HEA nanopillars.
基金supported by School of Engineering and Built Environment,Glasgow Caledonian University,National Natural Science Foundation of China(Nos.51405044,51105061 and 11472075)the EPSRC funded ARCHIE-WESt high-performance computer(www.archie-west.ac.uk)(No.EP/K000586/1)
文摘Persistent slip band(PSB) is an important and typical microstructure generated during fatigue crack initiation. Intensive work has been done to investigate the mechanisms of the formation of persistent slip bands since the 1950 s when Wadsworth[1]observed the fatigue fracture in copper. Simulations have indicated that PSBs formation during fatigue crack initiation is related to the dislocation driving force and interaction. In this paper, a molecular dynamics(MD) simulation associated with embedded atom model(EAM) is applied to the PSBs formation in nickel-base superalloys with different microstructure and temperature under tensiletensile loadings. Five MD models with different microstructure(pure γ phase and γ/γ phase), grain orientation([1 0 0][0 1 0][0 0 1]and [1 1 1][ 0 1][2 1]) and simulation temperature(300 K, 600 K, 900 K) were built up in these simulations. Our results indicated that within the γ phase by massive dislocations, pile-up and propagation which can penetrate the grain. Also, it is found that the temperature will affect the material fatigue performance and blur PSBs appearance. The simulation results are in strong agreement with published experimental test result. This simulation is based on the work^([2]). The highlights of the article include: 1) investigation of the PSB formation via molecular dynamics simulation with three different parameters, 2) conduct of a new deformation and velocity combination controlled simulation for the PSB formation, 3) high-performance computing of PSB formation, and 4) systematic analysis of the PSB formation at the atomic scale in which the dislocation plays a critical role.
基金the National Natural Science Foundation of China(Nos.51704209,U1810208,U1810122)the Central Government Guided Local Science and Technology Development Projects,China(No.YDZJSX2021A010)+5 种基金the Projects of International Cooperation in Shanxi Province,China(Nos.201803D421086,201903D421076)Shanxi Province Patent Promotion Implementation Fund,China(No.20200718)the Technological Innovation Programs of Higher Education Institutions in Shanxi Province,China(No.201802034)Shanxi Province Scientific Facilities and Instruments Shared Service Platform of Magnesium-based Materials Electric Impulse Aided Forming,China(No.201805D141005)Science and Technology Major Project of Shanxi Province,China(Nos.20191102008,20191102007,20181101008)Yantai High-end Talent Introduction“Double Hundred Plan”,China(2021)。
