Atomic-scale Simulation Study On Diffusion And Static Mechanical Properties Of Nickel-based Micro-laminated Composite Materials

Metal-based laminated composite materials with tough and brittle layers possess excellent comprehensive properties and strong designability,making them widely applicable.Nickel-based laminated composite materials are lightweight,high in strength and toughness,have high temperature resistance,and impact resistance.They can replace strategic high-temperature structural materials in key areas such as aerospace,national defense industry,and automotive industry.These composites play a protective role in important components such as aircraft engine turbine blades,supersonic aircraft intake ducts,micro-nano ignition devices,and medicine formwork.In this paper,we investigate the diffusion and static properties of Ni,Al,Ni/Al microstack composites and Ni/Ni3 Al microstack composites with the help of molecular dynamics.Firstly,molecular dynamics simulations reveal the role of Ni,Al stretching phenomenon and Ni/Al microstack nanostructures in mutual diffusion phenomenon,intermetallic compound formation and interfacial behavior,and reveal the relationship between dislocation length and stress-strain and the effect of solid solution treatment time on Ni/Al diffusion and properties.After that,the relationship between the plastic deformation mechanism of Ni/Ni3 Al microstack composites with preexisting hole size at the interface under tensile loading and the formation process of dislocations were investigated.Finally,the influence of the phase interface on the mechanical properties of Ni-based single-crystal alloys was investigated by nanoindentation.It is an important theoretical guidance for quantifying the structure-property relationship at the nanoscale and for the in-depth understanding of the mechanical properties of Ni-based single-crystal alloys and their engineering applications.Molecular dynamics simulation is used to reveal the tensile phenomenon of Ni,Al fixed area under a constant strain rate of 2×108 s-1.The relationship between dislocation length and stress-strain is basically inversely proportional.The rise of dislocation length at peak stress indicates the occurrence of stacking fault in layered structure,and also shows that pressure rod dislocations hinder dislocation diffusion in the system.Solid solution treatment was carried out on Ni/Al laminate composites for 20 ns compared to 0.5ns;Ni atoms diffused more fully forming Al3 Ni compound with a ratio of 25% Ni to 75% Al.The stress increased from 1.6 GPa to 1.9 GPa,and elongation increased by 30%.The existence of pre-pores has improved the performance of Ni/Ni3 Al material.The yield strength increases from13.3 GPa to 14 GPa when using 2? pore size for Ni/Ni3 Al laminate composites.Pore sizes ranging from 0-12? all improve tensile performance while starting decreasing at 15? pore size.Pre-existing small columnar pores help dissipate local energy caused by interface lattice mismatching,stress concentration effectively suppresses dislocation nucleation at the interface,and changes the normal state of dislocation decomposition to improve yield.The decomposition of full dislocations in the interface during tensile process explains the occurrence of dislocations.After stretching,atomic stress concentration and disorder occur at the Ni/Ni3 Al interface.Dislocation reaction causes stacking fault to occur near Ni and Ni3 Al layer interfaces.Tracking atomic motion explains the formation of dislocations and slip planes.The results show that a full dislocation in Ni/Ni3 Al interface decomposes into a pressure rod dislocation and two Shockley partials,the pressure of Stair-rod dislocation is fixed while Shockley partials slide outwards.When oriented properly,two Shockley partials will generate "Hirth locks" at their intersection.Frank’s defects exist as transition defects,and stacking faults are formed with FCC→HCP phase transformation.A nano-indentation test was performed on different phase interfaces of Ni/Ni3 Al laminate composites using a radius 4nm indenter.From P-h curve,atomic structure,and defect analysis,it is revealed that compared with pure nickel as matrix phase,Ni3 Al as strengthening phase has better mechanical properties and higher hardness values.The change trend of force generated when lifting up indenter mainly depends on material elastic recovery.Interface force produced when lifting up indenter mainly depends on material elastic recovery.The stronger elastic recovery,the greater interfacial force.Study shows that potential energy varies with indentation depth.Ni3 Al has much higher potential energy than other two phases.Side view proves that adding Ni3 Al can enhance laminated materials’ performance.By analyzing static mechanical properties of Ni/Al and Ni/Ni3 Al laminated composite materials,it is found that under tensile load,Pure Al area deforms or fractures indicating high strength after solid solution treatment for layered materials.Interfacial strength increases significantly which improves overall toughness.Performance improvement occurs regardless if pure nickel or pure aluminum were used.Tensile behavior shows that as Ni content in Al increases,the ultimate tensile strength and toughness of the alloy increase.The existence of micro-pores improves the performance of Ni/Ni3 Al material.Ni3 Al has a greater impact on the performance of Ni/Ni3 Al than other phases.