Copper Alloy Strip Research Articles

Effect of Low-Temperature Annealing on the Bending Properties of C19400 Copper Alloy Strips

Effect of Low-Temperature Annealing on the Bending Properties of C19400 Copper Alloy Strips

Nano-precipitates evolution and properties improvement mechanism of Cu–Zn–Ni–Si-X alloy strip based on multi-element microalloying and thermomechanical treatment

In this paper, we put a variety of elements into the Cu–Ni–Si alloy for smelting and processing, and systematically characterized and tested the microstructure, precipitates and service performance during the process. We found that adding Cr, Zr, Ti, and Mg led to grain refinement and produced some twin structures. In addition, based on Ni–Si precipitates, the generation of the nano-Cr3Si phase (50 nm in size) is promoted, and their distribution in the matrix is relatively uniform. The dispersed precipitates can effectively strengthen the service performance of the copper alloy, and the strength of the alloy exceeds 500 MPa while maintaining high conductivity. The research results of this paper can provide a basis for the design and development of copper alloy strips for new energy vehicle connections.

Effect and Mechanism of Solidified Microstructure on Deformation Behavior, Mechanical Properties, and Residual Stress of Cu-Ni-Si Alloy.

Cu-Ni-Si alloy is the key raw material for the lead frame of large integrated circuits. The disordered grain orientation of alloy billet, high hardening rate, residual stress, and poor surface quality of cold working strips seriously affect its processability. In order to improve the cold-working properties of Cu-Ni-Si alloy, two kinds of C70250 copper alloy strips were produced through hot mold continuous casting (HMCC) and cold mold continuous casting (CMCC) technology. The effects of solidified microstructure on the cold-working deformation behavior, mechanical properties, and residual stress of the alloy were studied. The results show that C70250 copper alloys with columnar grain and equiaxed grain were prepared through HMCC and CMCC. After a 98% reduction in cold rolling, columnar grain strip surface quality was very good, and the elongation was still as high as 3.2%, which is 2.9 times that of equiaxed grain alloy. The residual stress of equiaxed grain strips reached 363 MPa, which is 2.7 times that of columnar grain strips. During the cold rolling process, equiaxed grain strips are prone to cause intersecting plane dislocations, stacking faults, shear bands, and grain breakage during large deformation cold rolling. The columnar grain strip causes parallel plane dislocations, stacking faults, and shearbands. Furthermore, the deformation structure was found to be uniform, and, ultimately, the alloy formed a fibrous structure. Therefore, the elongation and latter distortion of columnar grain strips improved after being put through large deformation cold rolling, which greatly reduced residual stress.

The comprehensive performance and strengthening mechanism of the columnar crystal Cu-Ni-Si alloy after two large deformation rates of cryogenic rolling-aging

In order to improve the strength and electrical conductivity of Cu-Ni-Si alloy, the columnar crystalline C70250 copper alloy strip suffer from two deep cryogenic rolling-aging treatments with large deformation, and the relationship between the cryogenic rolling-aging process and microscopic structure, mechanical, conductive properties is studied, and the precipitation behavior is analyzed. The research findings show that the columnar crystalline C70250 copper alloy produced by continuous directional solidification can be directly processed by two cryogenic rolling-aging treatment with large deformation, eliminating the traditional solution treatment process and obtaining a fibrous tissue structures containing high-density dislocations and multi-scale precipitates, the yield strength, tensile strength and electrical conductivity of the alloy reached 879 MPa, 923 MPa and 38.7 % IACS respectively, combination of strength and electrical conductivity is excellent. Two deep cryogenic rolling with large deformation can force the matrix to change to amorphous, favorable to atomic diffusion. Solute atoms are continuously transformed into Ni2Si phase and Cu atoms are continuously expelled, forming large-sized pure Ni2Si precipitated phase and small-sized NiSi cluster phase containing Cu atoms, which together impede dislocation movement and reinforce alloy. With the uniform precipitation of multi-scale nano-precipitation phases and reduction of grain boundary density, the electrical conductivity along the rolling direction is significantly reduced.

High strength and high electrical conductivity C70250 copper alloy with fibrous structure reinforced by high density, multi-scale nano-precipitates and dislocation

Cu–Ni–Si alloy has a difficult combination of high strength and high electrical conductivity, which limits its further application in electronics industry. In this work, the effects of large deformation double cold rolling-aging processes on the microstructure, mechanical properties and electrical conductivity of the columnar grain alloy were studied, and its mechanism was revealed. The results show that the C70250 copper alloy strip prepared by hot mold continuous casting technology can be directly subjected to large deformation double cold rolling-aging treatments without solid solution process. The excellent balance of tensile strength and electrical conductivity, as high as 884 MPa and 45.7% IACS, respectively, can be obtained for the alloy after primary 95% cold rolling and aging at 450 °C for 45 min followed by secondary 60% cold rolling and aging at 400 °C for 10 min. The strength and electrical conductivity is better than the similar products reported. The realization of high strength and high electrical conductivity is attributed to the interaction between strain hardening and precipitation behavior of columnar alloy during double deformation and aging treatment. The repeated introduction of large deformation cold rolling provides a new short diffusion driving force for the precipitation of solute atoms by GPA and APT results, the precipitation rate is increased in the second stage of aging. At the same time, the nanometer-sized strengthening phase formed by primary aging can effectively nail the dislocations formed in the secondary cold rolling process, and finally form a fibrous structure with uniform mixing of multi-scale nano cluster and Ni2Si phase. The strength of the alloy is significantly improved by dislocation strengthening and multi-scale precipitation strengthening. C70250 copper alloy precipitate as many solute atoms as possible, and retains fibrous structure, the dispersing of electrons by solute particles and grain boundary limits is fundamentally diminished, and the electrical conductivity is improved.

Effects of a thermal-ultrasonic stress relaxation process on the residual stress, mechanical properties and microstructures of C19400 copper alloy strips

With the development of 5G communication, more demanding requirements have been specified for copper alloy strips applied in lead frames. Thin copper alloy strips with high residual stress always warp during the etching process, so they do not meet the requirements of industry. Therefore, it is essential to reduce the residual stress in these strips. In this work, a novel effective technique suitable for thin strips, the thermal-ultrasonic stress relaxation (TUSR) method, which integrates conventional thermal stress relaxation (TSR) and ultrasonic stress relaxation (USR), is proposed. The equipment used to conduct TUSR and TSR experiments on C19400 copper alloy was produced in this laboratory. The residual stress evolution was investigated using X-ray diffraction (XRD). The microstructure evolution of the strips was analyzed by using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The mechanism of the relaxation of residual stress was revealed. The maximum residual stress relaxation values in the transverse and rolling directions after TUSR treatment were 80.56 and 89.39%, respectively, which were better than the results obtained after TSR treatment. After TUSR treatment, the grain sizes were smaller, and the percentage of low-angle grain boundaries (LAGBs) was higher than that before the treatment. The dislocation morphology was converted to ordered dislocation cells and dislocation walls and macroscopic plastic deformation of the grains released elastic strain energy, which was the main reason for residual stress relaxation in the C19400 alloy strips. In addition, the increase in tensile strength was mainly due to the enhancement of a precipitate pinning effect and grain refinement. These findings can provide guidance for future work related to the relaxation of residual stress in copper alloy strips for lead frames.

Effects of a Thermal-Ultrasonic Stress Relaxation Process on the Residual Stress, Mechanical Properties and Microstructures of C19400 Copper Alloy Strips

Effects of a Thermal-Ultrasonic Stress Relaxation Process on the Residual Stress, Mechanical Properties and Microstructures of C19400 Copper Alloy Strips

Effects of a Thermal-Ultrasonic Stress Relaxation Process on the Residual Stress, Mechanical Properties and Microstructures of C19400 Copper Alloy Strips

Effects of a Thermal-Ultrasonic Stress Relaxation Process on the Residual Stress, Mechanical Properties and Microstructures of C19400 Copper Alloy Strips

Improvement of experimental device for high cycle fatigue tests of copper alloy strips and characterizing fatigue properties

Improvement of experimental device for high cycle fatigue tests of copper alloy strips and characterizing fatigue properties

Improvement of experimental device for high cycle fatigue tests of copper alloy strips and characterizing fatigue properties

Improvement of experimental device for high cycle fatigue tests of copper alloy strips and characterizing fatigue properties

Electromagnetic forming of aluminum alloy strip by imposing inverse current instead of inducing eddy current

In the conventional electromagnetic forming processes, the Lorentz force is induced by the eddy current in the specimen, so the coil should be specifically designed to form the electrical current return. Here, a novel electromagnetic forming method is suggested for aluminum alloy strip or profile, in which the inverse current is imposed instead of eddy current to generate Lorentz force. As an electromagnetic actuator, a very simple strip of copper was connected in parallel with the aluminum alloy strip. When the impulse currents flowed synchronously along the opposite directions between the copper and aluminum alloy strips, the Lorentz force was generated to deform the aluminum alloy strip. The electromagnetic forming of AA5754 aluminum alloy strip by imposing inverse current was investigated by numerical simulation. It was finally validated by comparison with the experimental results.

Relationship and mechanism between double cold rolling-aging process, microstructure and properties of Cu–Ni–Si alloy prepared by two-phase zone continuous casting

Developing Cu–Ni–Si alloy with high strength and high electrical conductivity is a key issue in the electrical conductor industries. The C70250 copper alloy was prepared by two-phase zone continuous casting (TZCC) technology first, and then carried out by double cold rolling-aging process. The relationship between different double cold rolling-aging processes, microstructure, mechanical properties and electrical conductivity of the alloy was studied in detail, the mechanism was revealed. The results show that the C70250 copper alloy strip fabricated by TZCC technology can be subjected to large deformation double cold rolling-aging treatment. When the alloy is primary cold rolled by 97.5% reduction rate, primary aged at 400 °C for 30 min, second cold rolled by 60% reduction rate, second aged at 400 °C for 45 min, the tensile strength and electrical conductivity of the alloy can reach 879 MPa and 48.9% IACS respectively, owning excellent comprehensive properties. The Ni2Si phases inside C70250 copper alloy after primary aging effectively pin dislocations during the secondary cold rolling process, which forms high density dislocation entanglement, promotes the further precipitation of Ni2Si phase during the process of secondary aging, and finally produces a large number of fine, dispersed, multi-scale mixed and evenly distributed Ni2Si phases, the increase of alloy strength is mainly ascribed to dislocation and Orowan strengthening effect. Solute atoms inside the C70250 copper alloy get adequately precipitated after large deformation double cold rolling-aging treatment, the recrystallization is delayed, and the fibrous microstructure along the rolling direction is produced, the scattering effect of transverse grain boundaries and solute atoms on electrons is significantly reduced, which is helpful to improve the electrical conductivity of the C70250 copper alloy.

Thermal characteristics and uniformity of microstructures during temperature controlled mold continuous casting profiled copper alloy strip

Nonuniform temperature field at cross section of profiled billets during conventional continuous casting always results in serious defects and inhomogeneous microstructures. In this paper, a 3D temperature controlled mold continuous casting (TCMCC) model for preparing profiled copper strip was established and verified to calculate the magnetic and temperature field during continuous casting process. Under different controlled temperatures of TCM and casting speeds, the temperature fields in the TCM and melt were numerically calculated, and the variation of temperature fields in the mushy zone was analyzed. The calculated temperatures are in good agreement with the measured values. The results indicate the uniformity of temperature gradient (uG) at the profiled section improves significantly when the controlled temperature of TCM is higher than the liquidus temperature of alloy, further, the uG gradually reaches the minimum and then increases with increasing casting speed. Based on the calculated results, the profiled KFC copper alloy strips with good surface quality were successfully prepared by the TCMCC under controlled TCM temperature of 1423 K and casting speeds of 15–60 mm/min. The value of the uniformity of primary dendrite spacing at the cross section of the profiled strips reaches the minimum with the casting speed of 45 mm/min.

Relationship and mechanism between microstructure and property of C70250 copper alloy strip prepared by temperature controlled mold continuous casting

Temperature controlled mold continuous casting (TCMCC) technology was used to fabricate the C70250 copper alloy strips. The influences of solidification microstructure on mechanical and electrical properties of C70250 copper alloys were systematically studied, and the relevant influencing mechanism was discussed. The results show that the microstructure of TCMCC C70250 copper alloy has a large number of fine dispersed Ni2Si phases, small angle grain boundaries and columnar grains with strong [001] orientation. The tensile strength, elongation and electrical conductivity of the C70250 copper alloy are 328 MPa, 40.4% and 24.3% IACS, respectively, which are obviously higher than the properties of the C70250 copper alloys prepared by conventional cold mold casting methods. The tensile strength of TCMCC C70250 copper alloy strip significantly increases due to the dislocation plugging inside the grains, which caused by strong pinning effect of Ni2Si phases during room temperature tensile. Straight small angle grain boundaries and columnar grains with strong [001] orientation significantly reduce the hindering effect of grain boundaries on dislocations. The deformation between and within grains is more uniform, and it is not easy to form high strain concentration, which leads to the increase of plastic deformation ability. The scattering effects of solute atoms and transverse grain boundaries on electrons are significantly reduced due to the precipitated Ni, Si atoms and the high orientation of columnar grain structure, which contributes to the improvement of the electrical conductivity.

Effect of cold rolling reduction rate on mechanical properties and electrical conductivity of Cu–Ni–Si alloy prepared by temperature controlled mold continuous casting

The contradictory relation between the strength and electrical conductivity of Cu–Ni–Si alloy after cold deformation is a significant scientific issue, break the contradictory relation is an important challenge for preparing the Cu–Ni–Si alloy with high strength and electrical conductivity. The C70250 copper alloy strips were prepared by temperature controlled mold continuous casting (TCMCC) and cold rolled. The effects of different cold rolling reduction rates on mechanical properties and electrical conductivity of the alloy were investigated, and the mechanism was revealed. The results indicate that the C70250 copper alloy strip prepared by TCMCC can be directly cold rolled with large deformation. When the cumulative cold rolling reduction rate reaches 97.5%, the strength and electrical conductivity of the alloy increase by 327 MPa and 0.6 IACS%, respectively. With the increase of cold rolling reduction rate, the shear deformation degree of columnar grain structure with strong [001] orientation increases gradually in C70250 copper alloy prepared by TCMCC. The alloy forms a large number of parallel shear bands consisting of high density dislocations, which seriously hinder the slip of dislocations and lead to the continuous increase of strength of the alloy. The parallel distributed shear bands in the C70250 copper alloy uniformly cut the matrix during the cold rolling process, and finally form a fibrous-shaped microstructure. The transverse grain boundary density is significantly reduced after cold deformation, which greatly reduces the influence of transverse grain boundary on the electrical conductivity and leads to abnormal increase of the electrical conductivity of the alloy.

Effect of the Combined Heat Treatment and Severe Plastc Deformation on the Microstructure of Cunisi Alloy

Abstract The aim of this work was to study the microstructure and functional properties of CuNi2Si1 alloy. The material was prepared classically by melting, casting, hot rolling and cold rolling. The obtained strips were processed with combined operations of supersaturation, ageing and one of the intensive deformation method - repetitive corrugation and straightening. The efficiency of RCS operation in shaping of functional properties in precipitation hardened copper alloys depends not only on tool geometry and operating parameters but also on whether and at what stage of strip production the supersaturation operation was applied. Application of the supersaturation before RCS operation broadens the potential to shape the set of functional properties. Comparable functional properties of the precipitation hardened copper alloy strips can be reached without application of the supersaturation operation in their manufacturing processes. The process of RCS applied after annealing, and the potentially slightly lower mechanical properties would be compensated by higher electrical conductivity.

A Novel Algorithm to Scheduling Optimization of Melting-Casting Process in Copper Alloy Strip Production

Melting-casting is the first process in copper alloy strip production. The schedule scheme on this process affects the subsequent processes greatly. In this paper, we build the multiobjective model of melting-casting scheduling problem, which considers minimizing the makespan and total weighted earliness and tardiness penalties comprehensively. A novel algorithm, which we called Multiobjective Artificial Bee Colony/Decomposition (MOABC/D) algorithm, is proposed to solve this model. The algorithm combines the framework of Multiobjective Evolutionary Algorithm/Decomposition (MOEA/D) and the neighborhood search strategy of Artificial Bee Colony algorithm. The results on instances show that the proposed MOABC/D algorithm outperforms the other two comparison algorithms both on the distributions of the Pareto front and the priority in the optimal selection results.

Temperature Field Simulation of TP2 Copper Strip during Reversible Universal Hot Rolling Using Finite Element Method

As universal hot-rolling cogging can not only make full use of the alloy’s high temperature plastic but also has the characteristic of little deformation resistance, it can provide large volumes of heavy strip. Besides，Universal hot-rolling can reduce the materias of trimming effectively and improve material utilization. At present more than 90 percent of copper and copper alloy strip are manufactured by hot-rolling. The paper presents details of simulation and analysis of 3500×980×200-size copper strip in hot rolling process by using finite element simulation technique. Particular attention is paid to predict the temperature distribution and temperature history in each pass during the process.

Ultrafine Grained Copper Alloys Processed by Continuous Repetitive Corrugation and Straightening Method

A growing trend to use new copper-based functional materials is observed recently world-wide. Within this group of materials particular attention is drawn to those with ultrafine grain size of a copper matrix. This study was aimed to investigate mechanical properties, electrical conductivity and microstructure in strips of precipitation strengthened copper alloys processed by continuous repetitive corrugation and straightening (CRCS). Tests were performed with the copper alloy strips using original die set construction installed on tensile testing machine. The microstructure was investigated using optical and electron microscopy (TEM and SEM equipped with EBSD). Proposition of semi industrial application of this method have been also presented. The CRCS process effectively reduced the grain size of a copper alloy strips, demonstrating the CRCS as a promising new method for producing ultra fine grained metallic strips.

Bond strength evaluation of roll bonded bi-layer copper alloy strips in different rolling conditions

Roll bonding is a solid-state welding process to join similar and dissimilar metals and alloys and is widely used as a manufacturing process. In this study, bi-layer copper alloy strips were roll bonded at warm and cold conditions; and then the effects of parameters that create successful bonds, such as the amount of deformation by rolling and rolling temperature on the bond strength were investigated. For this purpose, faying surfaces were degreased and scratch brushed, being fractured coherently after entering roll gap at different reductions. As deformation proceeded and the roll pressure increased, these cracks quickly expanded into fissures. This process allowed the bond to be established between the underlying materials of the base metal layers, termed virgin metal, which were extruded through the cracks and fissures at the scratch brushed regions. The peel strengths of the bonds were measured and were found to increase when the rolling temperature or the thickness reduction are increased.