Saturation Dislocation Microstructures of Double-slip-oriented Copper Single Crystal during the Corrosion Fatigue in a 0.5 mol/L NaCl Aqueous Solution

Copper single crystal specimens with the longitudinal axis parallel to the [013] double-slip-orientation were grown through Bridgman technique. The fatigue tests were performed using a symmetric tension-compression load mode at room temperature in an open-air and a 0.5 mol/L NaCl solution, respectively. The dislocation microstructures were observed with scanning electron microscopy (SEM) by the electron channeling contrast (ECC) and transmission electron microscopy (TEM). The results show that the saturation dislocation microstructures during the corrosion fatigue in the aqueous solution of 0.5 mol/L NaCI, mainly consisted of labyrinth, wall and vein dislocation structures, which differs from the dislocation structures of the walls and veins in an open-air environment.

Multiscale simulation of nanometric cutting of single crystal copper——effect of different cutting speeds

A multiscale simulation has been performed to determine the effect of the cutting speed on the deformation mechanism and cutting forces in nanometric cutting of single crystal copper. The multiscale simulation model, which links the finite element method and the molecular dynamics method, captures the atomistic mechanisms during nanometric cutting from the free surface without the computational cost of full atomistic simulations. Simulation results show the material deformation mechanism of single crystal copper greatly changes when the cutting speed exceeds the material static propagation speed of plastic wave. At such a high cutting speed, the average magnitudes of tangential and normal forces increase rapidly. In addition, the variation of strain energy of work material atoms in different cutting speeds is investigated.

MULTIAXIAL BEHAVIOR OF NANOPOROUS SINGLE CRYSTAL COPPER:A MOLECULAR DYNAMICS STUDY

The stress-strain behavior and copper are studied by the molecular dynamics incipient yield surface of nanoporous single crystal （MD） method. The problem is modeled by a periodic unit cell subject to multi-axial loading. The loading induced defect evolution is explored. The incipient yield surfaces are found to be tension-compression asymmetric. For a given void volume fraction, apparent size effects in the yield surface are predicted： the smaller behaves stronger. The evolution pattern of defects （i.e., dislocation and stacking faults） is insensitive to the model size and void volume fraction. However, it is loading path dependent. Squared prismatic dislocation loops dominate the incipient yielding under hydrostatic tension while stacking-faults are the primary defects for hydrostatic compression and uniaxial tension/compression.

Relationships between the surface quality of a single crystal copper ingot and the process parameters of a heated mould continuous casting method

The relationships between the surface quality of a single crystal copper ingot and the process parameters of heated mould continuous casting method were studied experimentally using our own design of horizontal heated mould continuous casting apparatus, and the mechanism by which process parameters affect the surface quality of a single crystal copper ingot is analyzed in the present paper. The results show that the process parameters affect the surface quality of a pure copper ingot by affecting the position of the liquid-solid interface in the mould. The position of the liquid-solid interface in the mould must be controlled carefully within an appropriate range, which is determined through a series of experiments, in order to gain a single crystal copper ingot with good surface quality.

Process Parameters of Manufacturing Single Crystal Copper by Heated Mold Continuous Casting

The effect of process parameters on the surface quality of single crystal copper ingot was studied through experiment with a self-designed horizontal heated mould continuous casting apparatus,and the mechanism was analyzed.The results show that the process parameters affect the surface quality of pure copper ingot by affecting the position of the liquid-solid interface in the mould.The position of the liquid-solid interface in the mould must be controlled carefully in an appropriate range determined through experiments in order to gain a single crystal copper ingot with a high surface quality.

Molecular Dynamics Study on Wavefront Structure of Single Crystal Copper under Femtosecond Laser Loading

We used computer simulation with the advantage of easily designing the material structure to design single crystal copper samples,studied the mechanical behaviors of this material under different shock compression conditions,and comparatively analyzed the reasons for the formation of different mechanical behaviors.An important macro performance of metal mechanical behaviors under shock compression is the shock wave front.In fact,the structure and the evolution of the shock wave front during the plastic phase are determined by its microscopic process,i.e.,the development process of shear flow and energy dissipation in the plastic phase.Due to the limitation of the resolution of experimental instruments,it is not yet possible to obtain a clear shock wave front structure through experiments.By means of molecular dynamics(MD)simulation,we obtain the velocity and coordinate information of every atom in each system,then compare the plastic deformation behavior of the material under different impact conditions,and finally obtain the impact of the shock conditions on the structure of the shock wave front.

Microstructure and texture evolution of cold drawing <110> single crystal copper

By means of electron backscattering diffraction and transmission electron microscopy the microstructure and texture of drawn single crystal copper with initial orientation （110） parallel to axial direction have been investigated in the present work. In or- der to analyze the effect of initial orientation on microstructure and texture of drawn copper, the results of the drawn （110） sin- gle crystal copper wires have been compared with （100） and （111） single crystal copper wires. It is found that the grain subdi- vision of （110） single crystal is more evident than that of （100） and （111）, and the textures consisting of （111） and （100） abruptly form in the drawn （110） single crystal. At high strains, due to shear strain, the distribution of fiber textures is imho- mogenous along the radial direction of drawn （110） single crystal copper wires. （100） is near the surface and （111） is at the center. The microstructure results of drawn （110） single crystal show that at low strains, it can be characterized as two kinds of geometrically necessary boundaries with noncrystalline character. At medium strains, S bands can be observed. At high strains, lamellar boundaries form. Mean misofientation and average spacing of dislocation boundary are larger in drawn （110） single crystal, as compared with （111） and （100）. In drawn （110） single crystal with high strains, the bimodal distribution forms at lower strains than in drawn （100） single crystal, which is because the dislocation boundaries with high angle are contributed by not only the boundary between （111） and （100） fiber textures but also the boundary in （111） or （100） texture.

Material removal mechanism of copper chemical mechanical polishing with different particle sizes based on quasi-continuum method

In this paper,the material removal mechanism of copper chemical mechanical polishing was studied by the quasicontinuum method that integrated molecular dynamics and the finite element method.By analyzing the abrasive process of different particle sizes on single crystal copper,we investigated the internal material deformation,the formation of chips,the stress distribution,and the change of cutting force.Results showed that shear band deformation was generated along the cutting direction at approximately 45° inside the workpiece material.The deformation was accompanied by dislocations and sliding phenomena in the shear band region.Smaller abrasive particle size led to poor quality of the workpiece,while a larger particle size led to better quality.However,larger particle size resulted in greater plastic deformation and deeper residual stress inside the workpiece.Size change of abrasive particles had little effect on the tangential cutting force.

Formation and capturing of nanoparticles in Cu-1wt.%Fe alloy melt during directional solidification process

A single crystal Cu-1wt.%Fe alloy with finely dispersed iron-rich nanoparticles which keep coherent interface with the copper matrix was prepared under directional solidification.Formation of nanoparticles in the alloy melt was investigated by performing differential scanning calorimeter tests and designed water quenching experiment at a certain temperature.Results show that iron-rich nanoparticles are formed in the Cu-1wt.%Fe alloy melt before primaryα-Cu forms,which is not consistent with equilibrium phase diagram.Mechanism that iron-rich nanoparticles are uniformly captured in the matrix was described,which is that numerous nanoparticles follow Brownian motions and are engulfed in the solidified matrix which makes it possible to form uniformly distributed nanoparticles reinforced single crystal Cu-1wt.%Fe alloy.