Alumina Dispersion Strengthened Copper Alloys Research Articles

Characteristics and Strengthening Mechanism of Texture Induced By Large Plastic Deformation for Nanostructured Alumina Dispersion Strengthened Copper Alloys

The characteristics and strengthening mechanism of the texture induced by large plastic deformation of alumina dispersion strengthened copper with 0.1 wt% Al content were investigated by electron backscattering diffraction (EBSD), transmission electron microscope (TEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) instrument and universal tensile testing machine. The outcomes show that the texture developed by hot extrusion with large plastic deformation is a main double fiber texture of 70% 〈001〉//X and 19% 〈111〉//X along the deformation direction (X-direction), as well as random orientations of a low fraction (11%). However, the random orientations can be completely transformed into {112} 〈111〉 Copper texture by cold work with large plastic deformation. The resulting texture reaches a 100% double fiber texture containing 70% 〈001〉//X and 30% 〈111〉//X fiber textures, and possesses high thermo-stability and high tensile strength. It can is therefore concluded that the enhanced fiber texture is an important reason for tensile strength improved by the cold work, except for grain refinement and increasing dislocation. The fiber texture strengthening is controlled by both morphology strengthening and orientation strengthening.

Strength and electrical conductivity behavior of nanoparticles reaction on new alumina dispersion-strengthened copper alloy

Alumina dispersion-strengthened copper (ADSC) alloy is a new materials widely used in lead frames, resistance welding electrodes, etc. The paper has systematically studied the strength and electrical conductivity behavior in situ reaction using rare-earth La and Ce. Solving the clustering on nanoparticles Al2O3 under spark plasma sintering (SPS) and addition of La and Ce for ADSC alloy is the significant differences. Specimen of Cu-0.7 wt% Al2O3 added with 0.7 wt% Ce does not present pores in SEM and BSE images due to special dispersed element Ce. A new ADSC alloy fabricated with Cu-0.7 wt%Al2O3-0.7 wt% Ce under SPS shows the high -strength and the high-conductivity. Nanoparticles Al2O3 encircled with nanoparticles CeO2 and Cu2O, which is generated in situ are evenly distributed in the Cu matrix, resulting in increasing strength. Lattice distortion does not occur in the new ADSC alloy. Cu atoms are replaced by Al generated in situ to form a solid solution with a face-centered cubic structure owing to the similar atomic radii and electronegativities of Cu and Al, resulting in increasing the electrical conductivity. Experimental results show that adding rare-earth metal nanoparticles Ce can significantly improve the properties of ADSC alloy.

Microstructure evolution of alumina dispersion strengthened copper alloy deformed under different conditions

Microstructure and texture evolution of Cu–0.23%Al2O3 dispersion strengthened copper alloy, deformed at room temperature or cryogenic temperature, were investigated. The main textures in hot-extruded specimen were Brass {011} <211> and Cube {100} <100>. Textures of Brass {011} <211> and Goss {011} <100> were observed in specimen after deformation at room temperature; while textures of Brass {011} <211>, Goss {011} <100> and S {123} <634> were detected after deformation at cryogenic temperature. It is believed that the additional Al2O3 nanoparticles can result in dislocation pinning effect, which can further lead to the suppression of dislocations cross-slip. While in the specimen deformed at cryogenic temperature, both pinning effect and cryogenic temperature are responsible for the formation of Brass, Goss and S textures.

High temperature mechanical behavior of alumina dispersion strengthened copper alloy with high content of alumina

The microstructure and its effects on the high temperature mechanical behavior of Cu–2.7%Al2O3 (volume fraction) dispersion strengthened copper (ADSC) alloy were investigated. The results indicate that fine alumina particles are uniformly distributed in the copper matrix, while a few coarse ones are distributed on the grain boundaries. Tensile tests results show that Hall-Petch mechanism is the main contribution to the yield strength of ADSC alloy at room temperature. Its high temperature strength is attributed to the strong pinning effects of alumina particles on the grain and sub-grain boundaries with dislocations. The ultimate tensile strength can reach 237 MPa and the corresponding yield strength reaches 226 MPa at 700 °C. Tensile fracture morphology indicates that the ADSC alloy shows brittleness at elevated temperatures. Creep tests results demonstrate that the steady state creep rates at 400 °C are lower than those at 700 °C. The stress exponents at 400 °C and 700 °C are 7 and 5, respectively, and the creep strain rates of the ADSC alloy are controlled by dislocation core diffusion and lattice diffusion.

Characteristics of alumina particles in dispersion-strengthened copper alloys

Two types of alumina dispersion-strengthened copper (ADSC) alloys were fabricated by a novel in-situ reactive synthesis (IRS) and a traditional internal oxidation (IO) process. The features of alumina dispersoids in these ADSC alloys were investigated by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. It is found that nano-sized γ-Al2O3 particles of approximately 10 nm in diameter are homogeneously distributed in the IRS-ADSC composites. Meanwhile, larger-sized, mixed crystal structure alumina with rod-shaped morphology is embedded in the IO-ADSC alloy. The IRS-ADSC composites can obtain better mechanical and physical properties than the IO-ADSC composites; the tensile strength of the IRS-ADSC alloy can reach 570 MPa at room temperature, its electrical conductivity is 85% IACS, and the Rockwell hardness can reach 86 HRB.

Development of Research and Application of Copper Alloys with High Strength and High Conductivity

High-strength and high-conductivity copper alloy is a kind of structural function materials, which has excellent comprehensive mechanical and physical properties. The strengthening methods of copper alloy are summarized. The basic requirements of high-strength and high-conductivity copper alloy is established. The application of the materials is described, including lead frame materials, electrified contact wires materials, electrode Materials. Meanwhile, the alumina dispersion strengthened copper alloy is introduced. The internal oxidation process, structure, dispersoid and anti-intenerate properties have also been analysis in detail. Finally, the development direction of this material is put forward.

Properties and Fabrication of Alumina Dispersion Strengthened Copper Alloy with High Softening Temperature

Cu-Al2O3 alloy combine both high electronic conductivity and high softening temperature. Cu-Al2O3 alloy was fabricated by internal oxidation and hot extrusion methods in the present investigation. Microstructure and properties of Cu-Al2O3 alloy was studied. The influence of preparation parameters, hot extrusion parameters and heat treatment on the properties of the alloy was investigated. The results indicated that the grain of the alloy was very small with a size between 2-10μm. Softening temperature of the Cu-0.6% Al2O3 alloy and Cu-1.0% Al2O3 alloy was 900. Cu-0.6%Al2O3 alloy and Cu-1.0% Al2O3 alloy meeting the requirements for electrode in resistance welding is the ideal substitution of the traditional electrode materials for resistance welding.

Influence of Ag Impurity Doping on the Microstructure and Hardness of Alumina Dispersion Strengthened Copper Alloys

Dispersion strengthened copper alloys (DSC) with high strength and high conductivity are widely used in automobile and electronics industries. In the present investigation the influence of Ag impurity doping on the mechanical properties of the alumina dispersion strengthened copper alloys was studied by mechanical alloying, and the influence mechanism was discussed subsequently. Alumina dispersion strengthened copper alloys powder was fabricated by high-energy ball milling. XRD results showed that the high-energy ball milling can dissolve Al2O3 into Cu matrix. As-milled powder was consolidated by cold-pressing and sintered at 860oC, 900oC, 940oC and 980oC, respectively. It was shown that the addition of Ag can significantly improve the hardness of Cu alloys. SEM characterization showed that the size of Al2O3 particles in Cu-Al2O3 sintered at 980oC was about 200nm, which is bigger than the initial size (about 150±30nm) of Al2O3 particles; and the size of Cu-Al2O3-Ag sintered at 980oC and 860oC was about 100nm and 30nm respectively. The difference in alumina size was considered as the result of Ag segregation at Cu/ Al2O3 interface. The segregation of Ag at Cu/ Al2O3 interface can suppress the growth of Al2O3, which will significantly improve the hardness of Cu alloys.

Microstructural features and properties of high-hardness and heat-resistant dispersion strengthened copper by reaction milling

The oxide dispersion strengthened copper alloys are attractive due to their excellent combination of thermal and electrical conductivities, high-temperature strength and microstructure stability. To date, the state-of-art to fabrication of them was the internal oxidation (IO) process. In this paper, alumina dispersion strengthened copper (ADSC) powders of nominal composition of Cu-2.5 vol%Al2O3 were produced by reaction milling (RM) process which was an in-situ gas-solid reaction process. The bulk ADSC alloys for electrical and mechanical properties investigation were obtained by sintering and thereafter hot extrusion. After the hot consolidation processes, the fully densified powder compacts can be obtained. The single γ-Al2O3 phase and profile broaden effects are evident in accordance with the results of X-ray diffraction (XRD); the HRB hardness of the ADSC can be as high as 95; the outcomes should be attributed to the pinning effect of nano γ-Al2O3 on dislocations and grain boundaries in the copper matrix. The electrical conductivity of the ADSC alloy is 55%IACS (International Annealing Copper Standard). The room temperature hardness of the hot consolidated material was approximately maintained after annealing for 1 h at 900 °C in hydrogen atmosphere. In terms of the above merits, the RM process to fabricating ADSC alloys is a promising method to improve heat resistance, hardness, electrical conductivity and wear resistance properties etc.

Effect of cold rolling on properties and microstructures of dispersion strengthened copper alloys

Mechanical properties and microstructures of unidirectionally and tandem rolled alumina dispersion strengthened copper(ADSC) alloys under different conditions were investigated by tensile test, optical microscopy(OM), transmission electron microscopy(TEM) and scanning electron microscopy(SEM). For unidirectionally rolled ADSC alloys, their strengths and elongations in the longitudinal direction are higher than those in the transverse direction under both cold rolling and annealing conditions. Once fracture appears in their longitudinal stress—strain curves, sudden reduction of overall stress level before complete fracture can be observed in the transverse tensile curves. The anisotropy of mechanical properties for the ADSC alloy can be greatly improved by tandem cold rolling. And no sudden reduction of overall stress level appears in the stress—strain curves for tandem rolled ADSC alloys. The differences of their microstructures and tensile fractures were analyzed. In order to compare the differences of tensile fracture mechanism in different directions, longitudinal and transverse fracture models for unidirectionally rolled ADSC alloys were also introduced.

Tensile fracture behavior characterization of dispersion strengthened copper alloys

To well characterize alumina dispersion strengthened copper (ADSC) alloys, much work has been performed, while the effect of cold working methods on their microstructures and tensile fracture behaviors in the different directions, and corresponding fracture mechanism have not been studied systematically. In order to carry out such a systematic study, unidirectional and tandem rolling techniques were used to the ADSC alloys. The differences of tensile fracture behaviors between longitudinal and transverse directions for unidirectional rolled ADSC alloys are significant. Their mechanical properties and microstructures in longitudinal and transverse directions were studied. The C–G fracture mechanism was used to explain a sudden reduction of overall stress level in the transverse tensile curves for the unidirectional rolled ADSC alloys. Two fracture models were introduced to describe fracture processes. To reduce mechanical property anisotropy of ADSC alloys, a tandem rolling technology was proposed. Experimental results show this technology can significantly reduce the anisotropy.

Work softening characterization of alumina dispersion strengthened copper alloys

The effect of cold rolling on the hardness and microstructure of alumina dispersion strengthened copper (ADSC) alloys and oxygen free pure copper was investigated. With increased cold rolling deformation, a work softening phenomenon can be observed in ADSC alloys. The higher the alumina content is, the more difficult it is to observe the work softening phenomenon. This phenomenon is not observed in oxygen free pure copper, even after cold rolling 90%. The microstructural changes of the ADSC alloys were analyzed by TEM as a function of deformation. Initially, with an increase of the cold rolling deformation, a large number of dislocation cells are formed. Then, with further increased deformation, both a decrease of dislocation density and the formation of the smaller dislocation cells (subgrains) within the larger dislocation cells or the elongated bands are observed. Finally, as deformation attains a certain value, the smaller dislocation cells (subgrains) begin to coalesce, and the work softening phenomenon appears. All of these changes are the result of the interaction between the alumina particles and the dislocation line segments. In order to analyze the work softening mechanism for the ADSC alloys, a model is introduced in the paper.

Braze joints of dispersion strengthened copper

Prior attempts to join alumina dispersion strengthened alloys (GlidCop) to itself, stainless steel (SS) and other materials have been less than successful. Typically these joints show low strength and poor ductility due to the segregation of alumina particles at the braze interface. This paper presents the results of a study undertaken to develop low activation brazing alloys, fluxes and processes for vacuum, argon and air environments to join alumina dispersion strengthened copper alloys to 304 SS. Vacuum and argon experiments were conducted using a Gleeble resistance heated system. Air brazing experiments were conducted in a resistance heated furnace with active fluxes. A reactive braze alloy composition has been developed which eliminates the segregation of Al 2O 3 particles at the braze interface and produces joints with excellent strength and ductility. Wetting and mechanical properties of the braze alloys were measured. Tensile properties, microstructure, microhardness and measurements of the compositional segregation across the braze joint are discussed.