Drawn Copper Wire Research Articles

Prediction of Hardness in Drawn Copper Wire by Effective Strain from Finite Element Simulation

The study developed a hardness-strain reference curve to be used with the finite element simulation for the prediction of the hardness in the drawn copper wire. The hardness values of the deformed copper specimens from tensile tests were analyzed to construct a relationship between hardness and strain. By using an industrial wire drawing machine, a copper wire was drawn by 5 passes to reduce its diameter from 8 to 4.64 mm. All drawing dies used the same configurations which include an area reduction ratio of 20 percent, an approach angle of 7°, and a bearing length of 0.5 times the feeding wire diameter. The finite element simulations of the wire drawing processes were also performed to predict the effective strains in the drawn copper wires. With the use of the developed hardness-strain curve, the hardness of the drawn wires can be estimated. The results show that the difference between the predicted and measured hardness values is about 10 percent lower in the early stage of the wire drawing process, and the difference increases with the number of passes to about 30 percent higher in the later stage of the process.

Modelling recrystallization textures driven by intragranular fluctuations implemented in the viscoplastic self-consistent formulation

This paper presents a recrystallization model driven by intragranular orientation gradients and strain energy fields calculated by means of the viscoplastic self-consistent (VPSC) formulation. The VPSC model is extended for calculation of the coupling between intragranular stress fluctuations with corresponding second moments of lattice spin and misorientation fields in the grains. Access to these quantities allows modelling of transition bands and nucleation kinetics. In the proposed recrystallization model, grain growth is assumed to be proportional to the difference between the stored energy of each grain and that of the effective medium. Recrystallization textures for several cubic metals are simulated, showing good agreement with corresponding experiments. The model reveals the importance of considering appropriate, microstructurally-based and orientation-dependent recrystallization nucleation mechanisms. The recrystallization texture of heavily rolled copper with a strong cube texture component is found to be a consequence of nucleation at transition bands, which is also the cause of the recrystallization textures in compressed iron and drawn copper wire. In contrast, the recrystallization texture of rolled interstitial-free steel is found to be caused by grain boundary nucleation occurring in grains with the highest strain energy.

Primary Recrystallization Texture in FCC-Metal with Low Packing Defect Energy

The method of orientation microscopy (EBSD) is used to study the special features of recrystallization texture in drawn copper wire. It is shown that the strict crystallographic relationships between deformation and recrystallization orientations are consequences of the dominant role in structural transformations of special misorientations, i.e. special boundaries. Mechanisms of the appearance and “growth” of annealing twins are proposed.

Observation of Stress Corrosion Cracking of Semi-hard Drawn Copper Wire using Accelerated Aging

Observation of Stress Corrosion Cracking of Semi-hard Drawn Copper Wire using Accelerated Aging

Measurements of recrystallization kinetics by isochronal DSC in industrial drawn copper wires

The aim of this research is to study the kinetics of recrystallization and to determine various microstructural parameters after isochronal annealing of a cold-deformed copper wire by drawing. Appropriate measurement techniques were used such as differential scanning calorimetry(DSC) and X-ray diffraction (XRD). The refinement of XRD patterns was carried out by using the PM2k software. The energy stored by the dislocations and the activation energy were estimated by DSC under isochronal conditions using a different methods such as Kissinger, Ozawa, Boswell and Starink. In addition, the recrystallized fraction was determined as a function of temperature and some kinetic parameters. We noted that the increase of heating rates pushes up the recrystallization reaction. We observed a combined effect of the heating rate and the deformation level on the recrystallization parameters. When the heating rate and the deformation level are high then the recrystallization temperature, the stored energy by the dislocations, and the dislocation density will be high.

HEAT TREATMENT EFFECT ON THE CREEP OF INDUSTRIAL COPPER WIRE

Creep behavior of copper wire, produced by a wire drawing process, has been investigated by creep tests at 340°C under the stress 98,108 and 118 MPa. In this investigation, three samples have been tested: copper drawn wire non heat treated, and heat treated at 600°C and 700°C. Microstructure after the creep test was observed by optical microscopy to understand the rupture mechanism. We have found that the sample heat treated at 600 °C had a longer creep life. We have also deduced that the dislocation creep was the creep deformation mechanism of the drawn copper. SEM observations of fractured surfaces after creep tests of drawn copper wire non heat treated and treated 10 min at 600 °C under stress of 118 MPa.

New method for analyzing recrystallization kinetics of deformed metal by differential scanning calorimeter

The drawn copper wires have been analyzed by differential scanning calorimeter (DSC) and a new method, which uses DSC measurements to determine the Johnson-Mehl-Avrami-Kolmogorov (JMAK) exponent via introducing Arrhenius behavior and modifying the baseline of DSC curves, has been proposed. The results show that JMAK exponent and recrystallization activation energy of the drawn copper wires with a strain of 2.77 are about 2.39 and 125 kJ/mol, respectively. The line linking the tangency points of DSC curve hypotenuse can be used as the baseline when calculating recrystallization fraction. The JMAK exponent obtained by the DSC method is in a good agreement with that obtained by microhardness measurements. Compared to traditional methods to measure the exponent, the proposed method is faster and less labor intensive.

Prediction of grain deformation in drawn copper wire

Most copper wire is produced using a drawing process. The crystallographic texture of copper wire, which is strongly associated with grain deformation, can have a profound effect on the formability and mechanical and electrical properties. Thus, the ability to predict grain deformation in drawn copper wire could help to elucidate the evolution of microstructure, which could be highly valuable in product design. This study developed a novel method for predicting grain deformation in drawn copper wire based on finite element simulation with flow net analysis. Simple upsetting tests were conducted to obtain flow stress curves for the simulation of the drawing process. Predictions related to grain deformation were compared with those on the micrographs of the drawn copper wire obtained in experiments. In longitudinal and transverse cross-sections of the drawn wire, the predicted and experiment results presented similar trends involving considerable deformation within the grains. This preliminary study demonstrates the efficacy of the proposed method in providing information useful to the prediction of the grain deformation in drawn copper wire.

CONSTITUVE MODELLING FOR CREEP OF DRAWN COPPER WIRE

The high-temperature creep behaviour of drawn copper wire was studied by different constant stresses 98,108 and 118 MPa and under the temperatures of 250, 290 and 340°C. This study deals with the creep based prediction modelling of an industrial copper wire. The proposed unified creep damage constitutive equations were determined using experimental data achieved for materials at applied stress. The comparison of experimental and predicted effective creep strain curves is carried out for all applied stresses applied on the drawn copper wire. The evaluated stress exponent n = 9.21, 10 and 14 and the activation energy Q = 22.25, 31.75 and 50.75 indicated that the creep deformation of the drawn copper wire is controlled by the dislocation creep. The evaluated of the mean relative error from 5.18 % to 10.11 confirmed the creep strain predicted by the proposed model well agree with experimental data.

Heat Treatments Effect on the Mechanical Properties of Industrial Drawn Copper Wires

In this present investigation, the mechanical properties of industrial drawn copper wires have been studied by creep tests, tensile tests and hardness Vickers. The effect of prior heat treatments at 500°C for different time on the drawn wires behavior was the main goal of this investigation. We have found that these heat treatments influenced the creep behavior of drawn wires and recorded shape curves. The creep tests were applied under ambient atmosphere at 240 °C. The creep duration before rupture decreased with the prior heat treatment time. The creep tests results were confirmed by tensile tests. A relationship between the hardness and the ultimate tensile strength of this industrial material has been established. Optical and scanning electron microscopy observations have been also used. Cross section observations of the wire after tensile or creep-rupture tests have shown that the mechanism of rupture was mainly controlled by the void formation.

Investigation of the Effects of Lubricants Fat Content on Drawn Copper Wires

Investigation of the Effects of Lubricants Fat Content on Drawn Copper Wires

Effect of Transverse Grain Boundary on Microstructure, Texture and Mechanical Properties of Drawn Copper Wires

In the present study, microstructure and texture of drawn copper wires with a large number of transverse grain boundaries have been characterized and their mechanical properties have been analyzed. The results show that the texture evolution is accelerated by transverse grain boundary and the saturation value 60% of volume fraction of fiber texture component is reached rapidly with increasing strain. For the microstructure of drawn wires with a large number of transverse grain boundaries, the critical strain, where lamellar boundaries form, is less than that for wires with equiaxed grains or columnar grains (all grain boundaries parallel to axis direction). Since transverse grain boundary accelerates grain subdivision and dislocation density increases rapidly in drawn wires with a large number of transverse grain boundaries, there are a higher flow stress and a higher work hardening rate.

In Situ Electron Backscatter Diffraction Investigation of Recrystallization in a Copper Wire

The microstructural evolution of a cold drawn copper wire (reduction area of 38%) during primary recrystallization and grain growth was observed in situ by electron backscatter diffraction. Two thermal treatments were performed, and successive scans were acquired on samples undergoing heating from ambient temperature to a steady state of 200°C or 215°C. During a third in situ annealing, the temperature was continuously increased up to 600°C. Nuclei were observed to grow at the expense of the deformed microstructure. This growth was enhanced by the high stored energy difference between the nuclei and their neighbors (driving energy in recrystallization) and by the presence of high-angle grain boundaries of high mobility. In the early stages of growth, the nuclei twin and the newly created orientations continue to grow to the detriment of the strained copper. At high temperatures, the disappearance of some twins was evidenced by the migration of the incoherent twin boundaries. Thermal grooving of grain boundaries is observed at these high temperatures and affects the high mobile boundaries but tends to preserve the twin boundaries of lower energy. Thus, grooving may contribute to the twin vanishing.

Effect of Prior-Heat Treatments on the Creep Behavior of an Industrial Drawn Copper

The effect of prior-heat treatments at 500℃, 600℃ and 700℃ on the creep behavior of an industrial drawn copper has been studied under constant stresses (98, 108 and 118 MPa) and temperatures (290℃ and 340℃). The results revealed that the creep behavior and the creep life of the material depend strongly on these prior-heat treatments. The apparent activation energy Qc for different creep tests of a drawn copper wire was calculated. The fracture mechanism of the material is characterized using optical microscopy.

Analysis of temperature and speed effects on the drawing stress for improving the wire drawing process

This paper deals with experimental investigations in order to study the influence of drawing conditions on temperature rise and drawing stress in cold drawn copper wires. In the multipass drawing machine, the temperature rise and drawing stress are measured with thermocouples and load cell systems, respectively, for different drawing speeds. The results obtained show that the drawing stress and temperature rise vary during the drawing process. This certainly comes from the variation of the friction coefficient and the flow stress of the material depending on the drawing speed. From the experimental results, a relationship between temperature rise, drawing stress and friction coefficient is built. Based on this, a modification of Avitzur’s model is presented. This new model can help to select the process parameters which satisfy the conditions of minimum drawing stress for copper material.

Texture evolution and its simulation of cold drawing copper wires produced by continuous casting

The texture evolution of cold drawing copper wires produced by continuous casting was measured by X-ray diffractometry and electron back-scatter diffractometry, and was simulated using Taylor model. The results show that in the drawn poly-crystal copper wires produced by traditional continuous casting, 〈111〉 and 〈100〉 duplex fiber texture forms, and with increasing strain, the intensities of 〈111〉 and 〈100〉 increase. In the drawn single-crystal copper wires produced by Ohno continuous casting, 〈100〉 rotates to 〈111〉, and there is inhomogeneous distribution of fiber texture along radial direction of the wires, which is caused by the distribution of shear deformation. Compared with 〈100〉, 〈111〉 fiber texture is more stable in the drawn copper wires. Comparison of the experimental results with the simulated results shows that the simulation by Taylor model can analyze the texture evolution of drawn copper wires.

Nanostructure Formation during Deep Wire-Drawing of Copper

It was confirmed in the present study that deep drawing process in multi passes to produce fine wires of copper alloys can act as a kind of severe plastic deformation process. High purity copper was deeply wire-drawn up to an equivalent strain of 6.9, and microstructure evolution and change in mechanical properties were investigated. It was confirmed that deep wire-drawing process produced nanostructures composed of fiber-shaped ultrafine grains with a diameter of about 300 nm. The copper wires having nanostructures showed tensile strength of 480MPa, which was two times higher than that of the starting material. The microstructures and mechanical properties of the deep drawn copper wire were almost equivalent with those of the copper sheets severely deformed by ARB process, though there were some minor differences between two processes.

On the strain inhomogeneity in drawn copper wires

Three different wire drawing schedules were attempted to examine the effects of reduction of area, die-angle and friction coefficient on the strain inhomogeneity of drawn copper wires. The microhardness distribution was studied over the transverse and longitudinal cross-sections. Inhomogeneity factor (I.F.) curves; I.F. = f(r), I.F. = g(2α) and I.F. = h(μ) were determined from the measurements. The results indicate that less strain inhomogeneity is achieved in drawing wires through dies with low angle, low friction coefficient and high reduction of area. Despite the variation in reduction of area and die-angle, the strain was distributed evenly at the center of the drawn wires. Contrary to the existing theoretical models, inhomogeneity factor versus deformation zone geometry parameter (∆) was approximated by a second order polynomial curve and not a linear relationship, as was previously postulated. A new relationship was also proposed to relate the I.F. to the calculated redundant work factor Φ.

Role of Recovery in the Recrystallization Simulation Application to a Cold Rolled IF-Ti Steel and a Cold Drawn Copper Wire

A simple model including the recovery and nucleation kinetics is proposed to simulate recrystallization using a Monte Carlo technique. Nucleation is simulated on the basis of equations describing stored energy evolution and subgrain growth kinetics. The parameters describing the stored energy evolution during recovery are shown to influence not only the relative number, orientation and local distribution of nuclei, but also the recrystallization kinetics and the final texture. The estimated kinetics of nucleation, the mean stored energy evolution as well as the preferential texture of first nuclei are in agreement with experimental observations for annealing 40% cold-rolled IF-Ti steel and cold drawn copper wires.

Influence of Oxygen Content on the Static Recrystallization of ETP Copper

Cold-drawn Electrolytic Tough Pitch copper wires have been investigated with Neutron Diffraction and Electron Back Scattered Diffraction. The drawn copper wires (38% reduction in area) develop major <111> and minor <001> fiber textures. It appears that the texture intensity of the reinforcements within the <111> and <001> fibers is more pronounced in the center and intermediate part of the wires. During the first annealing time, it is found that the recrystallization kinetics is enhanced when oxygen content is increased. The recrystallized fraction within the intermediate zone of the wire is two times larger in the cathode with higher oxygen content. The mechanisms at the origin of this acceleration of recrystallization kinetics will be discussed taking into account the presence of Cu2O type oxides.