Deformation Behavior Of Cu Research Articles

Microstructure and hot deformation behavior of Cu–Ti–Zr(-Mg) alloys

In this study, the thermal deformation behavior of Cu–Ti–Zr(-Mg) alloys were investigated by Gleeble-1500D. The two alloys were deformed at 700–900 °C with 0.003–10 s−1 strain rate. The intrinsic equations of the two alloys were constructed and calculated thermal activation energies, which indicates that it is improved from 325.67 kJ/mol to 344.03 kJ/mol after Mg addition. The result showed that the hot working area of Cu–Ti–Zr alloy is greatly extended after Mg addition, and rheological instability area is reduced. The morphology of the alloys was observed to analyze thermal behavior. It revealed that Mg elements inhibited the occurrence of dynamic recrystallization and shifted the texture types in the alloys by characterization of EBSD. TEM results showed that the phases during hot deformation in Cu–Ti–Zr–Mg are Cu4Ti and Cu10Zr7, which are in a semi-coherent relationship with the Cu matrix.

Molecular dynamics simulations and analyzation of Cu deposited on stainless steel substrate surfaces

Copper (Cu) is used in integrated circuits and microdevices and has the potential to replace aluminum alloys due to its low resistivity, strong electromigration properties, and affordability. However, a significant factor that influences the performance of devices at the micro and nano scales is the surface roughness of the deposits. LAMMPS software is employed to simulate the deposition Cu on an ideal state for a stainless-steel substrate. The deposition process and deformation behavior of Cu on the surface and the roughness of the deposition surface are analyzed. Taking the deposition process of Cu atoms as an object, the effects of different atomic numbers, different temperatures, different velocities, and different heights on the surface roughness of the deposits were investigated. The atomic structure composition of the deposition velocity is analyzed, and the radial distribution function is analyzed to reveal the microscopic mechanism of action. The results of the theoretical deposition and analysis show that the surface roughness increases with the number of atoms deposited and decreases with increasing substrate temperature. The surface roughness first decreases and then, after some fluctuation, stays constant at a particular level with increasing velocity. Additionally, as the deposition height increases, the surface roughness reduces. There is a nonlinear relationship between the various components and the deposited surface roughness. The surface quality of deposits can be improved during the deposition process by optimizing the deposition parameters of deposition atoms, substrate temperature, deposition velocity, and deposition height.

Investigation of deformation comprised microstructure and precipitation of Cu–Sn–Ti alloy during hot deformation

The hot deformation behavior of Cu–Sn–Ti–(Cr) alloys was studied using Gleeble-1500D thermo-mechanical simulator ranging from 550 to 950 °C, and the strain rate was 0.001–10 s−1. The microstructure evolution of the alloy was analyzed using characterization methods such as electron backscatter diffraction (EBSD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Cu–Sn–Ti–(Cr) alloys were calculated by establishing the constitutive equation of the alloy. The activation energies of Cu–Sn–Ti and Cu–Sn–Ti–Cr alloys are 275.884 and 283.550 kJ/mol, respectively. The results indicate that the addition of Cr element has an inhibitory effect on the nucleation and improve refinement of dynamic recrystallization (DRX) in Cu–Sn–Ti alloy. The texture of Cu–Sn–Ti alloy is Cu texture at 750 °C and the texture contained in Cu–Sn–Ti alloy is Goss texture, Cubic texture and Cu texture when the temperature is raised to 950 °C. The texture of Cu–Sn–Ti–Cr alloy at 750 °C is Goss texture. The Goss texture transforms into Cubic texture and Cu texture when the temperature is raised to 950 °C. The precipitates present in Cu–Sn–Ti alloy include CuSn3Ti5 phase and Cu4Ti phase. The addition of Cr element adds a new phase of Cr to the alloy and also makes the distribution of precipitates more uniform and increases in quantity.

Study on microstructure evolution and hot deformation behaviour of Cu–6.5Fe–0.3Mg alloy

The hot deformation behaviour and microstructure evolution of the Cu–6.5Fe–0.3Mg alloy were explored. The optimum hot working temperature of the alloy was 950°C and the strain rate was 10 s−1. The alloy underwent dynamic recovery (DRV) and dynamic recrystallisation (DRX) behaviour during hot compression. The density of the Fe phase particles increased significantly, and they were all aligned along the vertical compression direction. The α-Fe phase transformed to γ-Fe phase at 950°C. A large amount of α-Fe and γ-Fe phases effectively inhibited the DRX behaviour of the Cu–6.5Fe–0.3Mg alloy and significantly improved its thermal stability. The research on the hot deformation behaviour of the Cu–6.5Fe–X alloys had a theoretical guiding role in determining its hot working process. Highlights The optimal hot deformation process of Cu–6.5Fe–0.3Mg alloy was clarified. Constitutive equations and thermal working diagrams of the alloys are constructed Thermal deformation significantly increases Fe particle density, optimising its distribution. the transformation of α-Fe phase to γ-Fe phase during the hot compression at 950°C. The increasing in Fe phase significantly inhibits the dynamic recrystallization of the alloy.

Plastic deformation behavior and constitutive modeling of Cu-50Ta alloy during hot compression

This paper presents a study on plastic deformation behavior of Cu–50Ta alloy at temperatures of 286–473 K and strain-rate of 0.01–6200 s−1. The effects of temperature, strain-rate, and strain on the yield strength, flow stress, and strain-rate sensitivity coefficient were determined. A phenomenological model was established to predict variation of the strain-rate sensitivity coefficient for Cu–50Ta alloy under dynamic compression. A Johnson–Cook constitutive model was established to predict the equivalent stress–equivalent plastic strain relationship under extreme deformation (high temperature and strain-rate). The results showed that the plastic deformation behavior of Cu–50Ta alloy was affected by temperature, strain-rate, and strain. The material exhibited obvious strain-rate strengthening and thermal softening. As the strain-rate increased, the yield strength logarithmically increased. At a temperature of 286 K, the strain-rate increased from 0.01 s−1 to 6200 s−1, and the yield strength increased from 543.75 MPa to 881.13 MPa. In addition, the yield strength linearly decreased as the deformation temperature increased. Under conditions of dynamic deformation, the variation of strain-rate sensitivity coefficient could be expressed as a function of strain-rate and strain. The phenomenological model accurately described the variation of the strain-rate sensitivity coefficient of Cu–50Ta under dynamic deformation conditions. The Johnson–Cook constitutive parameters, calibrated by experimental data, described the plastic deformation behavior of the alloy under high-velocity impact.

Deformation behaviour of Cu and Cu–Al in the dislocation starved regime: A molecular dynamics study

In general, with the addition of solutes, the yield strength of alloys is expected to increase; this phenomenon is known as solid solution strengthening. However, this model of strengthening implicitly assumes that dislocations are available and it is their motion that causes plastic deformation. On the other hand, in dislocation starved regimes, it is the nucleation of dislocations that controls the deformation behaviour. In this regime, the solute atoms can act as sites of heterogeneous nucleation for dislocations and “anomalous” softening with alloying additions are not uncommon. In this study, using Molecular Dynamics (MD) simulations, we show anomalous softening in Cu–Al alloys deformed at 300 K. We show that there are two components to this softening; in addition to the heterogeneous nucleation at solute sites, the reduction in stacking fault energy with alloying addition promotes the (homogeneous) nucleation of partial dislocation loops. In order to be consistent, we interpret the MD simulation results of deformation behaviour using parameters and energies derived from the same potentials used in the simulations. Specifically, we carry out the thermodynamic integration to evaluate the free energies in crystals with and without the stacking faults and hence calculate the SFE as a function of Al content at 300 K. Using the SFE values thus obtained, and using a continuum model of homogeneous nucleation of partial dislocation loops, we rationalise the deformation behaviour seen in pure copper. On the other hand, in Cu–Al alloys, the drop in yield strength can only be explained using a combination of the continuum model (which assumes homogeneous nucleation), and the reduction in heterogeneous nucleation barrier (which is a function of the ratio of the unstable and stable stacking fault energies). Thus, our results indicate that deformation experiments of pure copper and copper–aluminium alloys in the dislocation starved regime could be interesting and might show qualitatively and quantitatively different behaviour.

Role of solidification texture on hot deformation behavior of a Cu–Ni–Si alloy with columnar grains

Hot deformation behavior of an as-cast Cu–Ni–Si alloy with columnar grains in terms of flow stress, constitutive equation, processing map, microstructure evolution, and dynamic precipitation was investigated at deformation temperatures of 500 °C~800 °C and strain rates of 0.01 s−1~1 s−1. The results revealed that the true stress-strain curves of the as-cast Cu–Ni–Si rods exhibit continuously increased flow stresses. The relationships between the material parameters and strains were then modified by fourth power polynomial functions. Good fitness between the material parameters and strains was obtained. The constitutive equation derived using these relations predicts quite accurate values. Microstructure observed by confocal laser scanning microscopy, electron back-scattered diffraction, and transmission electron microscopy indicated that the main hardening mechanisms of the continuously increased flow stress are attributed to the progressively occurred dynamic recrystallization and dynamic precipitation. The dynamic precipitates, unlike in the aged alloys, are very fine and have multiple orientation relationships with the Cu matrix, which is likely linked with the change of edge-on habit planes due to the plastic deformation and temperature imposed. It has also been found that the processing map developed is also dependent on the strain selected. The processing maps developed at low strains contain larger instability regions than those developed at high strains, which agree with the results of microstructure observations.

Effect of Structural Relaxation on the Indentation Size Effect and Deformation Behavior of Cu–Zr–Based Nanoglasses

In this work, the deformation behavior of as-prepared (AP) and structurally relaxed (SR) Cu–Zr–based nanoglasses (NGs) are investigated using nano- and micro-indentation. The NGs are subjected to structural relaxation by annealing them close to the glass transition temperature without altering their amorphous nature. The indentation load, p, vs. displacement, h, curves of SR samples are characterized by discrete displacement bursts, while the AP samples do not show any of them, suggesting that annealing has caused a local change in the amorphous structure. In both the samples, hardness (at nano- and micro-indentation) decreases with increasing p, demonstrating the indentation size effect. The micro-indentation imprints of SR NGs show evidence of shear bands at the periphery, indicating a heterogeneous plastic flow, while AP NG does not display any shear bands. Interestingly, the shear band density decreases with p, highlighting the fact that plastic strain is accommodated entirely by the shear bands in the subsurface deformation zone. The results are explained by the differences in the amorphous structure of the two NGs.

Microstructure evolution and hot deformation behavior of Cu−3Ti−0.1Zr alloy with ultra-high strength

Abstract The hot compression deformation behavior of Cu–3Ti–0.1Zr alloy with the ultra-high strength and good electrical conductivity was investigated on a Gleeble–3500 thermal-mechanical simulator at temperatures from 700 to 850 °C with the strain rates between 0.001 and 1 s−1. The results show that work hardening, dynamic recovery and dynamic recrystallization occur in the alloy during hot deformation. The hot compression constitutive equation at a true strain of 0.8 is constructed and the apparent activation energy of hot compression deformation Q is about 319.56 kJ/mol. The theoretic flow stress calculated by the constructed constitutive equation is consistent with the experimental result, and the hot processing maps are established based on the dynamic material model. The optimal hot deformation temperature range is between 775 and 850 °C and the strain rate range is between 0.001 and 0.01 s−1.

Hot Deformation Behavior of Cu-Sn-La Polycrystalline Alloy Prepared by Upcasting.

In this study, the hot deformation of a Cu–0.55Sn–0.08La (wt.%) alloy was studied using a Gleeble-3180 testing machine at deformation temperatures of 400–700 °C and various strain rates. The stress–strain curve showed that the hot deformation behavior of the Cu–0.55Sn–0.08La (wt.%) alloy was significantly affected by work hardening, dynamic recovery, and dynamic recrystallization. The activation energy Q was 261.649 kJ·mol−1 and hot compression constitutive equation was determined as The microstructural evolution of the alloy during deformation at 400 °C revealed the presence of both slip and shear bands in the grains. At 700 °C, dynamic recrystallization grains were observed, but recrystallization was incomplete. In summary, these results provide the theoretical basis for the continuous extrusion process of alloys with promising application prospects in the future.

Деформационное поведение сплавов Cu–Al–Mn при воздействии температуры и механических напряжений

Деформационное поведение сплавов Cu–Al–Mn при воздействии температуры и механических напряжений

Accumulative roll bonding of Cu–Zr nanolaminate: Atomistic-scale investigation of structural evolution and grain orientation scatter dependence on rolling parameters

Understanding the role of processing parameters on the atomic-level deformation mechanism and structural evolution during an accumulative roll bonding process is a necessity in scaling-up the production of metallic nanolaminates. In this study, we have developed a novel atomistic model of “nano-rolling” to investigate the effect of roller speed and temperature on the deformation behavior of Cu–Zr nanolaminate. The model takes both the compressive and the shear forces into consideration during the rolling process, making it efficient in reproducing the actual deformation mechanisms. Results from the mobility analysis have shown that the final velocity of the rolled specimen obtained from the simulation is close to the theoretical value. The phenomenon of texture evolution is also analyzed through orientation scatter analysis, where it is revealed that increasing the roller speed facilitates the formation of low angle grain boundaries and twins at lower temperatures. However, texture weakening of the rolled specimen has been observed at elevated temperatures due to the increase in fine grained equiaxed structures. Concurrently, the roller speed and temperature dependent deformation mechanism of the Zr-layer is also captured through atomic displacement analysis, which shows the formation of a smooth and wavy Zr-layer. Through Voronoi analysis, it is revealed that the wavy profile of the Zr-layer has a direct influence on the formation of metallic glass at the Cu–Zr interface as a higher number of icosahedral clusters are observed in specimens with a wavy Zr-layer.

Atomic-scale investigation on the structural evolution and deformation behaviors of Cu–Cr nanocrystalline alloys processed by high-pressure torsion

Abstract A systematic investigation based on high-resolution transmission electron microscopy (HRTEM) and quantitative analysis was carried out to gain insights into the structural evolution and deformation behaviors of 57 wt%Cu - 43 wt%Cr dual-phase alloys deformed by high pressure torsion (HPT). Nanometer-sized grains were obtained, with Cu and Cr grain size being reduced from 33.7 nm to 17.4 nm and 35.6 nm to 18.6 nm respectively after deformation with 5 rotations and 25 rotations. During the early deformation stage, in a way, grain refinement in Cu was controlled by the interaction between Cr solutes (or clusters) that was forced to dissolve into Cu matrix and extended dislocations motion. At the higher strain condition, the deformation mode became more complicated and the grain refinement of Cu and Cr can be affected by solute effects and constraint effect during severe plastic deformation in this dual-phase system. In addition, inverse grain-size effect on stacking fault (SF) and twinning tendencies was observed in Cu under different deformation conditions. A critical grain size was calculated to describe the required shear stress for partial dislocation nucleation. HRTEM investigations and statistical analysis on twins observed in 25 rotations-strained sample reveal that the twins are associated with the grain boundary activities and the recovery procedure in the extremely fine grain size region. These atomic-scale observations provide new views in understanding the deformation mode, especially twinning behavior in the extremely fine grain size range below the critical grain size that are hardly obtained in experiments.

Influence of different precipitation states of Cu on the quasi-static and cyclic deformation behavior of Cu alloyed steels with different carbon contents

Cu precipitates in steels can lead to significant changes of mechanical behavior. However, most investigations focus on the influence of these precipitates on hardness, whereas the effects on quasi-static deformation behavior and cyclic properties remain unclear. Therefore, in the present work the deformation behavior of Cu alloyed steels with two different carbon contents, 0.005 and 0.2 wt%, was analyzed in tensile as well as fatigue tests. To characterize the influence of different precipitation states, various heat treatments were performed. The heat treatment parameters were chosen based on results obtained with the short-time procedure PhyBaLCHT, which is based on cyclic indentation tests and enables the determination of microhardness and cyclic hardening potential. The results reveal that a higher C content increases hardness, decreases cyclic hardening potential and leads to generally higher tensile strength. However, only at a shorter aging time does a higher C content increase fatigue strength, whereas at a longer aging time both steel variants show comparable fatigue lifetimes, despite the significantly higher hardness and tensile strength of the steel with higher carbon content. This can be explained with the higher cyclic hardening potential of the lower carbon steel, leading to an improved fatigue lifetime. Additionally, it could be shown for both steels that an increase of cyclic hardening potential, caused by longer aging times and different precipitation states of Cu, can be associated with increased fatigue strength. However, for an overall assessment of a material’s mechanical properties, both, hardness and cyclic hardening potential have to be considered.

Hot deformation behavior of Cu–Ni–Si alloy at elevated temperature

Hot compression tests of Cu–Ni–Si alloy with high Ni and Si contents were carried out on Gleeble-3800 thermal simulator in the deformation temperature of 750 °C ∼ 950 °C, strain rate of 0.01 ∼ 10 s−1 and deformation amount of 70%. Subsequently, constitutive equation based on Arrhenius-type constitutive model considering strain effect was established, and the average absolute relative error and correlation coefficient R were 7.34% and 0.991. Then, hot Processing map was obtained by combining the power dissipation and instability maps, and the suitable processing conditions could be predicted. Based on the results of these experimental and theoretical investigations on the hot deformation behavior of Cu–Ni–Si alloys, Multi-direction compression (MDC) was carried out at 860 °C and corresponding strain of single pass and accumulated 24 passes 0.4 and 9.6 respectively. The resulted microstructure consisted of fine matrix grains with a diameter of 3.02 μm and well dispersed Ni31Si12 particles 0.62 μm, suggesting that the results of thermal simulator and corresponding calculation were credible for guiding the thermo-mechanical processing parameters of Cu–Ni–Si alloys.

A modified constitutive model and hot compression instability behavior of Cu-Ag alloy

Abstract The hot compressive deformation behaviors of Cu−6wt.%Ag alloy were studied experimentally in the temperature range of 973−1123 K and the strain rate range of 0.01−10 s−1. The stress increases and reaches the maximum value when the true strain is very small, and then the stress changes slowly and tends to be stable under the action of work hardening, dynamic recovery and recrystallization. The material parameters of the conventional Arrhenius constitutive model are only related to strain under different deformation conditions, and the prediction error is large, which cannot accurately characterize the hot deformation behavior of the alloy. To describe the hot deformation behavior of the alloy accurately, a modified constitutive model was established by considering the simultaneous influence of forming temperature, strain rate and strain. The results indicate that correlation coefficient (R) and the average absolute relative error (AARE) are 0.993 and 4.2%, respectively. The modified constitutive model can accurately describe the hot deformation behavior of Cu−6wt.%Ag alloy.

Hot Deformation Behavior of Cu–9.83Ni–1.24Fe–0.7Mn–0.012Ce Alloy for Seawater Pipelines

The flow stress of a Cu–9.83Ni–1.24Fe–0.7Mn–0.012Ce alloy at high temperature is studied by using a thermo‐simulation machine. The microstructure is characterized by optical microscopy and transmission electron microscopy. The flow stress and strain increase linearly in the initial stages of hot deformation, and two trends exist after the linear section. When the strain rate exceeds 0.1 s−1, the flow stress continues to increase with an increase in deformation. When the strain rate is less than 0.1 s−1, steady‐state flow results. A thermal‐processing map of the alloy is established based on the dynamic material model. The destabilization zone of the alloy is established for 800–870 °C and a strain rate of 0.1–10 s−1. Subgrains are formed by dynamic recovery with high‐density dislocations. The deformation temperature range of safe processing I zone is 800–900 °C with a strain rate of 0.01–0.1 s−1; and the deformation temperature range of safe processing zone II is 900–1000 °C with a strain rate of 0.01–10 s−1. The softening mechanism of recrystallization is conducive to thermal processing.

Bifurcation in deformation behavior of Cu and Ta by accumulative roll-bonding at high temperature

Cu and Ta are co-deformed at 673K by the accumulative roll-bonding technique up to 8 passes. At an equivalent von Mises strain (ɛvm) of ~2 the deformation is bifurcated into shear accommodated by the ‘soft’ Cu, and plane-strain by the ‘hard-but-ductile’ Ta. This is attributed to transitions occurring collectively at ɛvm ~2 in crystallographic texture, partitioning of recovery and recrystallization, and the nature of interfaces as elucidated by orientation relations, Hall-Petch behavior and manifestation of instabilities at higher strain.

Effects of Ag Addition on Hot Deformation Behavior of Cu–Ni–Si Alloys

Hot deformation behavior of Cu–Ni–Si and Cu–Ni–Si–Ag alloys is investigated using the Gleeble‐1500D simulator in the 600–800 °C deformation temperature and 0.01–5 s−1 strain rate ranges. Dynamic recrystallization (DRX) mechanism is a feature of high temperature flow stress–strain curves of the alloy. Microstructure is observed by optical microscopy. Ag addition can refine the grains and accelerate dynamic recrystallization. Characteristic points of the flow stress curves, including critical strain for DRX initiation (ϵc), are determined by employing strain hardening rate analysis. Processing maps are developed and analyzed based on the dynamic material model (DMM). Ag addition can optimize the alloy processing workability.

Characterization of the Hot Deformation Behavior of Cu–Cr–Zr Alloy by Processing Maps

Hot deformation behavior of the Cu–Cr–Zr alloy was investigated using hot compressive tests in the temperature range of 650–850 °C and strain rate range of 0.001–10 s−1. The constitutive equation of the alloy based on the hyperbolic-sine equation was established to characterize the flow stress as a function of strain rate and deformation temperature. The critical conditions for the occurrence of dynamic recrystallization were determined based on the alloy strain hardening rate curves. Based on the dynamic material model, the processing maps at the strains of 0.3, 0.4 and 0.5 were obtained. When the true strain was 0.5, greater power dissipation efficiency was observed at 800–850 °C and under 0.001–0.1 s−1, with the peak efficiency of 47%. The evolution of DRX microstructure strongly depends on the deformation temperature and the strain rate. Based on the processing maps and microstructure evolution, the optimal hot working conditions for the Cu–Cr–Zr alloy are in the temperature range of 800–850 °C and the strain rate range of 0.001–0.1 s−1.