Microstructure Evolution Of Cu Research Articles

Effects of temperature on the microstructural evolution and mechanical properties of copper − bearing medium manganese steel during tempering

This work introduced the effects of higher tempering temperatures on the microstructural evolution of Cu − bearing medium Mn steel. After quenching steel at 860 °C for 1 h, it was tempered at 600, 640, and 670 °C for 2 h. The results indicated that the low − temperature impact toughness initially increased and then decreased, while the yield strength consistently decreased with increasing temperature. At a tempering temperature of 640 °C, the steel exhibited a relatively high content of reversed austenite and demonstrated the best low − temperature toughness and plasticity. The low − temperature toughness and plasticity of the steel significantly diminished, when the temperature exceeded 640 °C. This is because the degree of alloying element enrichment in the reversed austenite is reduced, accompanied by an increase in dislocation density and the formation of twins. These reversed austenites exhibit a diminished ability to hinder crack nucleation and propagation. The yield strength decreased with increasing temperature, primarily due to the coarsening of the Cu particles, which reduces their precipitation strengthening effect. This study advances the development of high − strength tough medium − manganese steels.

Effect of Cr Content on Hot Deformation Behavior and Microstructure Evolution of Cu–Cr–Ni Bridge Weathering Steel

The hot compression tests (T = 850–1100 °C, = 0.1–10 s−1) of Cu–Cr–Ni bridge weathering steel with different Cr content (0.46% (#1), 0.64% (#2)) were performed on Gleeble‐3800‐D thermomechanical simulator. The effects of Cr content on hot deformation and microstructure evolution are systematically investigated by the Arrhenius constitutive equation, processing map, electron backscatter diffraction technology, and transmission electron microscope. In the results, it is demonstrated that the increase of Cr content from 0.46% to 0.64% enhances the solution strengthening and inhibits the dynamic recrystallization of the experimental steels during hot compression, resulting in the increase of flow stress. The Arrhenius constitutive equation with strain compensation is constructed. The increase of Cr content results in an augmentation of hot deformation activation energy, rising from Q#1 = 358.47 kJ mol−1 to Q#2 = 396.79 kJ mol−1, causing the increase of deformation resistance of Cu–Cr–Ni bridge weathering steel in hot compression. The optimal hot processing window of #1 and #2 experimental steels is as follows: = 0.1–0.2 s−1, T = 1050–1100 °C, = 0.1–0.15 s−1, and T = 1050–1100 °C, the increase of Cr content leads to the narrowing of the hot processing window of the experimental steels.

Microstructure evolution and mechanical properties of Cu–9Ni–6Sn alloy during continuous cold deformation process

A Cu–9Ni–6Sn alloy bar with pronounced axial columnar grains and a diameter of 10.5 mm was fabricated by using directional solidification technology, which was directly cold-drawn into a superfine alloy wire with a diameter of 40 μm without intermediate annealing. The strength and microstructure evolutions of the Cu–9Ni–6Sn alloy during the cold drawing were studied. The results indicate that twinning is more likely to occur in fiber structures ranging from 60 to 120 nm. A dual-fiber structure consisting of <111> and <100> orientations formed after cold-drawing. Unexpectedly, a large number of deformation twins were discovered within the <111> fibrous texture and later transformed into detwinning structures, disrupting the axial fibrous texture. The generation of deformation twinning primarily results from Ni and Sn elements disrupting crystal symmetry and reducing stacking fault energy of the alloy and the formation of <111> texture. The combined effects of detwinning structures and dislocation wall induced work-softening of the alloy, enabling high-strain processing and ultimately yielding nanocrystalline grains, i.e., the Cu–9Ni–6Sn alloy underwent cold drawing with a high train of 11.23 and obtained an average grain size of ∼38 nm, which exhibited a tensile strength of 1453 MPa.

Precipitation behavior and properties change of Cu–3Ti–2Ni alloy during aging process

The microstructural evolution of Cu–3Ti–2Ni alloy under primary and secondary cold rolling combined aging was investigated through various characterization techniques including transmission electron microscopy (TEM), scanning electron microscope (SEM), and X-ray diffraction (XRD). Additionally, the electrical and mechanical properties during different stages of aging were examined to reveal the organizational changes and performance variations of Cu–3Ti–2Ni alloy under primary and secondary aging. This study revealed that the alloy exhibited optimal primary aging performance at 450 °C for 4 h, with a strength of 954 MPa and an electrical conductivity of 21.5 %IACS (International Annealed Copper Standard for Conductivity). In comparison to primary aging, both strength and electrical conductivity were effectively improved under secondary aging conditions. The optimum secondary aging process was determined to be aging at 400 °C for 3 h, resulting in a strength of 1133 MPa and an electrical conductivity of 24.2 %IACS. During the aging process, the matrix witnessed the formation of numerous elliptical disc-shaped NiTi and Ni3Ti phases. Notably, the interface of NiTi phases exhibited a stronger coherency effect compared to Ni3Ti. β′-Cu4Ti precipitated uniformly within the matrix during aging, enhancing the alloy's strength. A recovery and recrystallization process occurred during aging, leading to the formation of sub-grains within the matrix.

Synergistic effects of ultrasonic vibration and isothermal treatment on the peritectic transformation and microstructure evolution of Cu–Sn alloy

To facilitate and even complete the peritectic transformation, the ultrasonic vibration (USV) and isothermal treatment were applied to the solidification process of Cu–70Sn alloy. It was found that the peritectic transformation was difficult to carry out due to the limited atomic diffusion under the normal solidification condition. With the single isothermal treatment, the peritectic transformation could be enhanced to some extent, with a small amount of η phase (Cu6Sn5) formed relying on the coarse elongated primary ε phase (Cu3Sn), but the further prolongation of isothermal time led to the abnormally coarsening of microstructure. When the molten alloy was subjected to 1500W USV and 30 min isothermal treatment, the peritectic transformation was dramatically facilitated. The ultrasonic-induced effects of cavitation and acoustic streaming play an important role in the remarkable reduction in the curvature radius of primary ε phase, thereby enhancing the diffusion of Sn solute atoms from the liquid phase to the interior of ε phase at the following isothermal stage. Accordingly, the transformation degree of ε phase to η phase was increased up to 77 %, and there was a high volume fraction of primary ε phase could thoroughly complete the peritectic transformation.

Microstructure evolution and deformation mechanism with comparison of Ta-2.5 W and Cu under detonation load

The comparison of microstructure evolution of Cu and Ta-2.5 W liner during explosively formed projectile (EFP) formation was studied. The electron backscatter diffraction method (EBSD) was used to statistically characterize the microstructure of the liner before and after deformation. Both recycled EFPs show strong fiber texture and different degrees of recrystallization. The center of the recycled Cu EFP has strong <001> and <111> preferred orientations along the EFP axis, and the density of the texture changes with the deformation strain. Cu EFP has extensive dynamic recrystallization, up to 88%, which is considered to be a traditional dynamic recrystallization mechanism, the temperature is the main controlling factor in the refinement process. On the contrary, the recycled Ta-2.5 W EFP has a strong <101> fiber preferred orientation, and almost no dynamic recrystallization occurs, large strain deformation is the main factor for the microstructure fragment.

Shape memory properties and microstructure evolution of Cu–Al–Fe alloys with different Fe contents

Shape memory properties and microstructure evolution of Cu–Al–Fe alloys with different Fe contents

Microstructural evolution in shear-punch tests: A comparative study of pure Cu and Cu-Cr alloy

Understanding the mechanisms behind microstructural evolution during shear deformation has been a long-standing area of interest. However, establishing a connection between microstructure, mechanical properties, and the extent of shear deformation is challenging and requires refined experimental approaches. Shear-punch testing (SPT) provides a controlled method to introduce shear into small volumes of material that later can be subjected to detailed microstructural characterization. In this study, we utilize an SPT device to induce shear deformation to pure copper (Cu) and a binary copper-chromium (Cu-Cr) alloy. Electron backscatter diffraction and transmission electron microscopy were used to study the mechanisms of plastic deformation after SPT. Our results indicate that shear deformation of pure Cu produces a dense network of intercepting microshear bands upon sustained deformation. Twin boundaries in annealed Cu undergo transformation into high-angle grain boundaries due to simultaneous deviation from the axis-angle pair condition of 60° misorientation on [111] direction. The presence of 50 vol% Cr particles in the soft Cu matrix altered the shear deformation mechanism. Preferential deformation of the Cu matrix in Cu-Cr alloy led to accelerated shear-induced formation of low and high-angle grain boundaries and subsequent grain refinement. Comparatively, insignificant grain refinement occurred in pure Cu samples even at a strain ∼10 times larger (ε = 4.73) than that of the Cu-Cr case (ε = 0.42). This study sheds light on the microstructural evolution of Cu during shear deformation and highlights the significant influence of a hard second phase in modifying the microstructural response mechanisms of a softer matrix.

High temperature deformation behaviour and microstructure evolution in Cu containing High Strength Low Alloy (HSLA) steel

ABSTRACT The hot deformation behaviour of a Cu containing high strength low alloy (HSLA) steel has been evaluated by carrying out hot compression tests over a temperature range of 900 °C to 1100 °C and constant true strain rates of 0.0003 to 1 s−1. Although single peak flow curve is observed predominantly, a tendency to exhibit multiple peaks at low strain rates (0.0003 and/or 0.001 s−1) at temperature greater than 950 °C. The important parameters pertaining to dynamic recrystallisation (DRX), such as critical, peak, steady state stress and strain were ascertained, and the DRX state diagram depicting the variation of critical parameters governing DRX with Zener-Hollomon parameter Z was established. The volume fraction of recrystallised grains, computed from flow stress, as expected, follows a sigmoidal trend indicating higher kinetics at low strain rates for a given temperature. Reconstruction of prior austenite grain boundaries (PAGB) based on electron back scattered diffraction (EBSD) technique for a few select specimens clearly elucidated the effect of temperature and strain rate on the DRX behaviour of the steel. The DRX state diagram established here clearly demarcates the deformation space i.e. temperature-strain rate-stain space into regimes where the material exhibits full DRX, hardening/softening + DRX and only hardening (no DRX) behaviour. This would be useful for designing suitable forging sequence to achieve the desired microstructure and mechanical properties.

Ce Effects on Deformation‐Induced Microstructure Evolution in Cu–Ti–Ni–Mg Alloys

Cu–Ti–Ni–Mg and Cu–Ti–Ni–Mg–Ce alloys are prepared by vacuum induction melting. The hot deformation tests of the two alloys are carried out on the Gleeble‐1500 simulator under the deformation temperatures of 550–950 °C and strain rates of 0.001–10 s−1. The true stress–strain curves of the two alloys are obtained and the constitutive equations are established. The activation energy of the Cu–Ti–Ni–Mg alloy is 344.02 kJ mol−1, and the activation energy of the Cu–Ti–Ni–Mg–Ce alloy is 389.87 kJ mol−1. Based on the processing maps, the optimal processing parameters of the two alloys are obtained. The microstructure of the two alloys is analyzed by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The addition of Ce reduces the dislocation density and texture strength. The CuNi2Ti precipitates are found in both alloys, and there are more precipitates in the Cu–Ti–Ni–Mg–Ce alloys. The addition of Ce increases the flow stress and activation energy, promotes precipitation, and improves the deformation resistance of the alloys.

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.

Effect of undercooling on microstructure evolution of Cu based alloys

Based on the deep undercooling rapid solidification method, the Cu based alloy has reached different undercooling degrees. The microstructure and evolution of non-equilibrium solidification of two alloys were systematically studied. It is found that grain refinement occurs in both the large undercooling range and the small undercooling range of the two alloys. EBSD technology was used to analyze the grain refinement structure, and the results showed that the grain refinement structure with large undercooling and that with small undercooling had completely different grain orientations. The grain refinement of low undercooling alloy is caused by dendrite remelting and fragmentation, while that of high undercooling alloy is completed by stress induced recrystallization. The evolution law of undercooling and microstructure hardness was systematically studied by using a microhardness tester. It was found that a sudden drop in grain size occurred near the critical undercooling, which is the direct evidence of grain refinement of non-equilibrium solidification structure of high undercooling alloy due to recrystallization.

Microstructure evolution and mechanical behavior of copper through‑silicon via structure under thermal cyclic loading

The through‑silicon via (TSV) technique is widely applied in the latest highly integrated circuits packaging. However, one of the prevalent failure modes is caused by thermal cyclic loading from power fluctuations of the chip. Different thermal expansion coefficients of Cu and Si could cause a mismatch of thermal stresses under temperature cycling, which will lead to thermal fatigue failure of structure. In the current study, thermal cycling experiments are performed on Cu-TSV samples to investigate the effect of temperature cycling on microstructure evolution and mechanical behavior. The electron backscatter diffraction analysis is conducted to investigate the grain size, local texture and microstructure evolution of Cu. Based on the crystal plasticity theory, a constitutive model considering temperature and grain size effect is developed, and the parameters are calibrated. Combining crystal plasticity theory and finite element analysis, the effects of grain orientation and different grain sizes on the stress distribution and plastic work evolution of TSV structure under thermal cyclic loading are investigated.

The effects of Nb additions on the microstructure evolution in Cu–9Ni–6Sn alloy

Cu–9Ni–6Sn specimens with different Nb contents ranging from 0 to 0.22 wt% were prepared by a vacuum induction furnace, and needle-like NbNi3 particles were found at the grain boundaries and interior after solution treatment. The results indicated that these NbNi3 particles suppressed the discontinuous precipitation (DP) growth during aging treatment. By using Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation and Arrhenius equation, the kinetics of DP is also figured out and the activation energy (Q) of the DP in Cu–9Ni–6Sn-xNb (x = 0, 0.05, 0.22 wt%) alloys are 75.8 kJ/mol, 80.9 kJ/mol and 88.5 kJ/mol, respectively, indicating that the atom diffusion for producing DP is more difficult in Nb-bearing alloys, and the formation of DP is inhibited correspondingly. What's more, the lamellar spacing (S) of DP increased and the growth rate of DP decreased in the with the Nb-bearing Cu–9Ni–6Sn alloy.

The special chemical short-range order and solidification behavior of Cu–Fe–P immiscible alloys

In this study, the featured local structure units and microstructure evolution of Cu–Fe–P immiscible alloy were investigated. Based on the first principle molecular dynamics simulation, it was revealed that P atoms were inclined to connect with Fe due to higher binding force. The special clusters containing P were determined in the forms of (5Cu + 5Fe) P, (6Cu + 4Fe) P and (5Cu + 5Fe) P at 1773 K, 1523 K and 1273 K, respectively. Based on the XRD analysis, it was found the Cu–32Fe–8P immiscible alloy was composed of Cu, Fe2P and Fe3P phases. Through a series of the collision, growth and coagulation motions, an evolving core-shell structure was observed in this ternary immiscible alloy. Controlled synthesis of Fe–P spheres with and without pores could be achieved with phase extraction of Cu–32Fe–8P alloys, which provides a novel route for the control formation and the wider potential application of functional phosphides.

Investigation of mechanical properties and microstructural evolution in Cu─Al alloys with gradient structure

Gradient structured (GS) materials have been reported to exhibit an outstanding mechanical properties. However, the influence of processing parameters on the GS specimens with different stacking fault energies (SFEs) and microstructural evolution during tensile are not very clear. In the present work, GS Cu─Al alloys with different SFEs of 28, 12 and 6 mJ/m2 were prepared by surface mechanical attrition treatment (SMAT) for different processing times. Results revealed that the SFE of 6 mJ/m2 specimen for SMAT 15 min exhibited a superior combination of strength and ductility, which had a significant hetero-deformation induced (HDI) stress originating from the accumulation of geometrically necessary dislocations (GNDs). Microstructure observations showed that deformation twins in the SFE of 6 mJ/m2 specimens formed in the gradient layer owing to its lower SFE. Moreover, in-situ electron backscatter diffraction (EBSD) revealed that the GNDs of the SFE of 6 mJ/m2 specimen initially formed at the grain boundaries with gradient grain size. Then, the formation of GNDs gradually migrated to the coarse grain region with increasing strain, which resulted in the HDI strain hardening and HDI stress strengthening. This work provide strategies to optimize properties and an understanding of deformation mechanisms in the GS materials during tensile test.

Effect of solute Mn on microstructural evolution of Cu–Mn alloys processed by equal channel angular pressing

Effect of solute Mn on microstructural evolution of Cu–Mn alloys processed by equal channel angular pressing

Formation mechanism of Cu/Cu3Sn–Cu/Cu interconnections based on solder-filled microporous copper as interlayer via a current-assisted thermal compression bonding

In this study, a Cu/Cu3Sn–Cu/Cu interconnection can be achieved based on solder-filled microporous copper (MPC) as interlayer via a current-assisted thermal compression bonding. The high-temperature soldering connection materials can be used in the third-generation semiconductor packaging, so as to meet the promising application in high-temperature power device packaging. The influence of auxiliary current on the microstructure evolution of Cu–Sn IMCs and its formation mechanism were studied. Experiments show that the action of Joule heat coupled with the electron wind significantly enhanced the interfacial reaction at the Cu/Sn metallization interface. The microstructure of Cu6Sn5 changed from scallop-like into columnar due to constitutional supercooling, and the dispersion distribution of Cu6Sn5 also changed. The growth constitutive equations of Cu3Sn in bondlines were established under current-assisted thermal compression bonding process.

Microstructural Evolution of Cu–Mn Alloys Processed by ECAP

Microstructural Evolution of Cu–Mn Alloys Processed by ECAP

Microstructure Evolution in Cu–0.5 wt% Zr Alloy Processed by a Novel Severe Plastic Deformation Technique of Rotational Constrained Bending

In the present study, a coarse-grained Cu–0.5 wt% Zr alloy was repeatedly processed by a novel technique of rotational constrained bending (RCB). In this technique, the workpiece was deformed by bending in a channel with an angle of 90°, using a rotating roller. The influence of the number of passes (N) of RCB on strain distribution, microstructure evolution and mechanical properties of the alloy was investigated. The heterogeneous distribution of the microhardness in the billet cross-section after the first pass was transformed into a homogeneous one after twelve passes, due to the rotation of the sample by 90° clockwise between individual passes. In addition, the gradual refinement/homogenization of the microstructure and formation of strong (110) crystallographic texture were found with increasing N. The initial grain size of 180 μm decreased down to 3.4 μm after twelve passes. The dislocation density increased by two orders of magnitude after RCB processing. In accordance with the grain-size refinement and the strong increase of the dislocation density, RCB processing significantly enhanced the strength of the alloy, while the ductility considerably decreased. The yield stress increased from 63 to 524 MPa, while the elongation to failure decreased below 10% after twelve passes.