Minor Addition Of Cu Research Articles

Precipitation strengthening and thermal stability in a conventionally non-heat treatable AA3xxx aluminium alloy

We report an unexpected yet significant precipitation-strengthening effect with remarkable thermal stability in an otherwise conventionally non-heat treatable AA3104 aluminium alloy. We reveal that a minor addition of Cu plays a critical role in the alloy's strength and thermal stability, and explain the underpinning mechanisms. The primary strengthening β′ phase can be engineered to exhibit distinctive structural characteristics, including regularly-spaced Cu atom columns at the coherent β′/Al interfaces, stacking faults and resultant domains. Our atomistic simulations rationalise that these microscopic characteristics are directly promoted by the Cu addition. The Cu-decorated interfaces promote β′ phase nucleation and result in strong, directional covalent-like Cu-Si bonding at the β′/Al interfaces. Specifically, the interfacial Cu columns increase the work of separation of the habit-plane interfaces and reduce the interface energy, resulting in significant strengthening and stabilising effects. The Cu columns also facilitate the stacking fault formation in the β′ phase. Collectively, these features enhance the strengthening effect and thermal stability of the precipitates. This study demonstrates the potential for exploring "new" features in "old" alloys to advance alloy science and technology.

Atomic Structure of Hardening Precipitates in Al-Mg-Si Alloys: Influence of Minor Additions of Cu and Zn.

Shifting toward sustainability and low carbon emission necessitates recycling. Aluminum alloys can be recycled from postconsumer scrap with approximately 5% of the energy needed to produce the same amount of primary alloys. However, the presence of certain alloying elements, such as copper and zinc, as impurities in recycled Al-Mg-Si alloys is difficult to avoid. This work has investigated the influence of tiny concentrations of Cu (0.05 wt %) and Zn (0.06 wt %), individually and in combination, on the precipitate crystal structures in Al-Mg-Si alloys in peak aged and overaged conditions. To assess whether such concentrations can affect the hardening precipitate structures, atomic resolution high-angle annular dark-field scanning transmission electron microscopy and atom probe tomography were adopted. The results indicate that low levels of Cu or Zn have a significant influence. Both elements showed a relatively high tendency to incorporate into precipitate structures, where Cu occupies specific atomic sites, creating its own local atomic configurations. However, Zn exhibited distinct behavior through the formation of extended local areas with 2-fold symmetry and mirror planes, not previously observed in precipitates in Al-Mg-Si alloys. Incorporation of Cu and/or Zn will influence the precipitates' electrochemical potential relative to matrix- and precipitate-free zones and thus the corrosion resistance. Furthermore, the presence of Cu/Zn structures (e.g., β'Cu, Q'/C) enhances the thermal stability of these precipitates and, accordingly, the mechanical properties of the material. The results obtained from this work are highly relevant to the topic of recycling of aluminum alloys, where accumulation of certain alloying elements is almost unavoidable; thus, tight compositional control might be critical to avoid quality degradation.

Age-hardening response of AlMgZn alloys with Cu and Ag additions

A recurrent challenge with aluminum alloys is their longstanding trade-off between mechanical strength and formability. Recently recyclability has put further pressure on the development of single-alloy concepts for solving this challenge. This study addresses an AlMg-based system featuring additional elements to facilitate age-hardening but retaining a high Mg content for inherent pronounced strain hardening as a potential candidate. Age-hardening was enabled by T-phase based precipitation in the commercial alloy EN AW-5182 via the addition of 3.5 wt.% of Zn. The investigation shows that minor additions of Cu and Ag enhance and accelerate it. The study also compares single-step and double-step artificial aging. Hardness and tensile testing and scanning transmission electron microscopy methods were deployed to characterize the alloys investigated, mechanically and microstructurally. An alloy with added Zn, Cu and Ag showed improved strain hardening and reduced serrated flow in the soft state, while exhibiting an age-hardening response of up to 326 MPa in yield strength leading to an ultimate tensile strength of 550 MPa in peak-aged condition. The study discusses the evolution of the microstructure during artificial aging in the light of Zn, Cu and Ag additions and their effect on the precipitation process.

The effect of Cu minor addition on the non-isothermal kinetic of nano-crystallites formation in Fe41Co7Cr15Mo14Y2C15B6 BMG

In this research, the effect of minor addition of Cu on the non-isothermal crystallization kinetic of Fe41Co7Cr15Mo14Y2C15B6 BMG was studied by using DSC technique at various heating rates of 5, 10, and 20 K min−1. The results of XRD and FE-SEM represented that the morphologies of nano-crystallites changed by addition of Cu. Also, triple kinetics parameters including activation energy (E), pre-exponential factor (A), and reaction model (g (α)) of this solid-state process were determined by using Starink and Friedman isoconversional, IKP, and fitting methods. The obtained activation energies showed that the BMGs have the highest GFA among Fe-based BMGs. Also, all various stages of crystallization process of this BMG were controlled by Avrami–Erofeev.

Age-Hardening Response of AlMgZn Alloys with Cu and Ag Additions

A recurrent challenge with aluminum alloys is their long-standing trade-off between mechanical strength and formability. Recently recyclability has put further pressure on the development of single-alloy concepts for solving this challenge. This study addresses an AlMg-based system featuring additional elements to facilitate age-hardening but retaining a high Mg content for inherent pronounced strain hardening as a potential candidate. Age-hardening was enabled by T-phase based precipitation in the commercial alloy EN AW-5182 via the addition of 3.5 wt.% of Zn. The investigation shows that minor additions of Cu and Ag enhance and accelerate it. The study also compares single-step and double-step artificial aging. Hardness and tensile testing and scanning transmission electron microscopy methods were deployed to characterize the alloys investigated, mechanically and microstructurally. An alloy with added Zn, Cu and Ag showed improved strain hardening and reduced serrated flow in the soft state, while exhibiting an age-hardening response of up to 326 MPa in yield strength leading to an ultimate tensile strength of 550 MPa in peak-aged condition. The study discusses the evolution of the microstructure during artificial aging in the light of Zn, Cu and Ag additions and their effect on the precipitation process.

Ductile Co-based bulk metallic glass with superhigh strength and excellent soft magnetic properties induced by modulation of structural heterogeneity

The development of Co-based bulk metallic glasses (BMGs) with satisfying comprehensive properties, including large glass-forming ability, high strength, large plasticity and excellent soft magnetic properties, is in high need for applications as structural and functional materials. A (Co0.7Fe0.2Ni0.1)67.7B21.9Si5.1Nb5Cu0.3 BMG with a record large plasticity of 5.5%, a high fracture strength of 4770 MPa, and a large critical diameter of 3.5 mm is successfully developed. This BMG also shows good soft magnetic properties, i.e. low coercivity (Hc) of 1.33 A/m and higher saturation magnetization (Bs) of 0.60 T. The enhanced strength and plasticity, as well as high Bs of this BMG, are all attributed to the minor addition of Cu in (Co0.7Fe0.2Ni0.1)68-xB21.9Si5.1Nb5Cux (x = 0, 0.1, 0.3, 0.5 and 0.7 at.%) system. The reduced average atomic spacing in the BMG, which comes from the squeezed spacing between Co, Fe, Ni and Nb atoms with proper addition of Cu, results in the improvement of fracture strength and Bs. The atomic-scale structural heterogeneity with the formation of crystal-like order structures is induced in the amorphous matrix, and thus the plasticity of (Co0.7Fe0.2Ni0.1)67.7B21.9Si5.1Nb5Cu0.3 BMG increases in spite of the decreased average atomic spacing.

Bacterially-mediated supergene alteration and redistribution of copper in mineralised rocks at the Salobo IOCG deposit, Brazil

The primary ore at the giant Salobo iron oxide copper-gold (IOCG) deposit in Brazil is dominated by magnetite and Fe-rich silicates, with minor (~1%) disseminated Cu-Fe sulphides and a distinctive absence of pyrite. Supergene Fe-silicate and sulphide oxidation has been mediated by bacteria, commonly within micrometre-scale acidic environments, but silicate-dominated acid neutralisation has maintained ambient circumneutral pH. Supergene Cu mobility has been controlled by the highly localised Fe-dominated biogeochemical processes, with Cu redistribution on the micrometre to metre scales and negligible supergene Cu enrichment. Silicates, especially the phyllosilicates biotite and chlorite, have variably altered to the clay minerals vermiculite and/or smectite, and ultimately to kaolinite. Leaching of Mn, Fe, Mg and Si accompanied silicate alteration, with minor addition of Cu to clay mineral structures and along cleavage planes. Iron mobilised by bacterial oxidation processes initially precipitated as ferrihydrite (with up to ~10 wt% Cu). Most Cu and Mn, mobilised in localised acidic environments, were precipitated nearby (metre scale) at circumneutral pH and reflect the immediate supergene biogeochemical environments: Cu-carbonates, pseudomalachite, chrysocolla, and Cu-Mn oxides (= “copper wad”). The early stages of these natural supergene processes were simulated in laboratory leaching studies using a range of fresh rocks inoculated with an endemic iron-oxidising strain of Acidithiobacillus ferrooxidans previously cultured from the Salobo site. Bacterially-mediated precipitation of ferrihydrite, commonly Cu-bearing, in these experiments strongly resembles that seen in the natural outcrops. These leaching experiments confirmed the effectiveness of silicate-dominated acid neutralisation, especially when accompanied by bornite oxidation, which is also acid-consuming. In contrast, chalcopyrite oxidation is acid-producing and leads to more effective localised Cu mobility in solution. Our combination of field and laboratory observations at the Salobo IOCG deposit shows that the biogeochemical environment dominated by Fe-silicates with little sulphides, typical for these systems, has led to an entirely different style of supergene Cu redistribution from that seen at many other Cu deposits, such as chalcopyrite and pyrite-rich porphyry copper deposits, where substantial supergene Cu enrichment has occurred.

Effect of Cu Presence on Evolution of Mechanical and Magnetic Properties in a Novel Fe-Based Bulk Metallic Glass During Partial Annealing Process

Fe-based bulk metallic glasses (BMGs) often demonstrate extremely poor toughness at room temperature, which seriously limit their widespread application. This study is focused on the improvement of mechanical properties (especially toughness) and ferromagnetic manner of a new Fe-based BMG by using partial annealing and minor addition of Cu as an alloying element simultaneously. The results revealed that the volume fraction of crystalline phases increased with the minor addition of Cu during the partial annealing process. Therefore, maximum hardness and toughness were observed in the alloy with 0.25 at. pct Cu after annealing within a temperature range of the fourth crystallization stage due to the high Poisson’s ratios (υ) of this element and the presence of nano-crystalline phases in the amorphous matrix with an optimal average size. Also, saturation magnetization of the as-cast BMG increased with the minor addition of Cu due to the formation of short-range order regions. While with addition of Cu, this magnetic parameter was reduced in annealed alloys due to an increase in the concentration of non-magnetic Cu atoms around the α-Fe nano-crystals.

Enhanced glass forming ability, mechanical, and magnetic properties of Fe41Co7Cr15Mo14Y2C15B6 bulk metallic glass with minor addition of Cu

In this study, enhancement of glass forming ability (GFA) as well as mechanical and magnetic properties of a Fe-based bulk metallic glass (BMG) was investigated with minor addition of Cu. The obtained results revealed that appropriate addition of Cu could significantly improve GFA of the base BMG. Furthermore, the mechanical properties of the investigated BMG were improved by the addition of 25 at.% Cu due to the positive heat of mixing between Cu and Fe atoms, decreasing the free volume and density of porosities. Therefore, the relatively good and comprehensive properties of the BMG containing 0.25 at.% Cu were exhibited; also, as a result of an excellent combination of good GFA (ΔTx = 48 K), microhardness (1425 HV), failure strain (εf = 2.1%), and failure strength (σf = 4400 MPa) was created it as a promising candidate for engineering applications. Furthermore, the magnetic measurements revealed that ferromagnetic properties of this Fe-based BMG decreased with the addition of 0.25 at.% Cu, but increased significantly with the addition of 0.5 at.% Cu.

Tailoring Morphology and Size of Microstructure and Tensile Properties of Sn-5.5 wt.%Sb-1 wt.%(Cu,Ag) Solder Alloys

Transient directional solidification experiments, and further optical and scanning electron microscopy analyses and tensile tests, allowed the dependence of tensile properties on the micromorphology and length scale of the dendritic/cellular matrix of ternary Sn-5.5Sb-1Ag and Sn-5.5Sb-1Cu alloys to be determined. Extensive ranges of cooling rates were obtained, which permitted specific values of cooling rate for each sample examined along the length of the casting to be attributed. Very broad microstructural length scales were revealed as well as the presence of either cells or dendrites for the Ag-containing alloy. Hereafter, microstructural spacing values such as the cellular spacing, λ c, and the primary dendritic spacing, λ 1, may be correlated with thermal solidification parameters, that is, the cooling rate and the growth rate. While, for the Cu-containing Sn-Sb alloy, the β-Sn matrix is characterized only by the presence of dendritic arrangements, the Ag-containing Sn-Sb alloy is shown to have high-velocity β-Sn cells associated with high cooling rate regions, i.e., positions closer to the bottom of the alloy casting, with the remaining positions being characterized by a complex growth of β-Sn dendrites. Minor additions of Cu and Ag increase both the yield and ultimate tensile strengths when compared with the corresponding values of the binary Sn-5.5Sb alloy, with a small reduction in ductility. This has been attributed to the homogeneous distribution of the Ag3Sn and Cu6Sn5 intermetallic particles related to smaller λ 1 characterizing the dendritic zones of the ternary Sn-Sb-(Cu,Ag) alloys. In addition, the Ag-modified Sn-Sb alloy exhibited an initial wetting angle consistent with that characterizing the binary Sn-5.5Sb alloy.

Amorphous phase stability and the interplay between electronic structure and topology

It is well-known that the stability of Pd-Si amorphous alloys can be improved substantially by minor additions of alloying elements such as Cu and Ag. Such improvement in stability is explained herein, whereby microscopic models based on efficient atomic packing and electronic structure were applied to the results of first principles simulations of Pd82Si18, Pd77.5Si16.5Cu8 and Pd75Si15Cu7Ag3 metallic glasses. It was revealed that while the atomic packing model fails to unequivocally explain the stabilizing effect of the binary Pd-Si alloy due to minor additions of Cu and/or Ag, the contribution of electronic states with lower energies to the stability of the amorphous structure is increased markedly. Further, the observed enhancement in the compressive ductility as a result of the addition of Ag to the Pd77.5Si16.5Cu8 alloy can be correlated to the combined effects of an increased heterogeneity in the local topology, weakened covalency and, hence, reduced directionality of Pd-Pd bonds as well as enhanced metallicity in the Pd75Si15Cu7Ag3 amorphous alloy. The analysis was further expanded to amorphous alloys where their characteristic binary prototypes are synthesised from late transition metals and non-metals as well as those comprising early transition metals and late transition metals. The findings shed light on the effects of minor alloying on the cooperative and competitive relationship between the topological and electronic structure of amorphous alloys.

The effect of undercooling on the microstructure and tensile properties of hypoeutectic Sn–6.5Zn–xCu Pb-free solders

Abstract Hypoeutectic Sn–6.5Zn alloy may be regarded as a better choice than eutectic Sn–9Zn lead-free solder in microelectronics industry. In this study, the properties of hypoeutectic Sn–6.5Zn lead-free solder were modified with minor additions of Cu. SEM investigations reveal that the plain Sn–6.5Zn solder exhibits large number of undesirable acicular structure of angular needle-like Zn particles at the solder matrix. The acicular-shape morphology of Zn was remarkably suppressed after Cu modification. Moreover, a new type of small flower-like γ-Cu5Zn8 intermetallic compound (IMC) was detected with 0.5 wt.% Cu added specimens. The flower-like morphology of γ-Cu5Zn8 IMC appears to cause a sharp increase in Young’s modulus, yield strength (YS) and ultimate tensile strength (UTS) of Cu modified solder. However, this effectiveness is reduced when 1.5 wt.% Cu addition starts to enhance the growth of coarse dendrite morphology of γ-Cu5Zn8 phase with enlarged β-Sn matrix. In addition, a 1.5 wt.% Cu addition was found to induce undesirable effects on the degree of undercooling, melting temperature and pasty range. Constitutive Garofalo model was assembled based on the experimental data of Sn–6.5Zn lead-free solders.

Effects of minor Cu addition on glass-forming ability and magnetic properties of FePCBCu alloys with high saturation magnetization

The effects of minor addition of Cu on glass-forming ability (GFA), thermal stability and magnetic properties of (Fe0.8P0.09C0.09B0.02)100− x Cu x (x = 0–1) alloys were investigated. The introduction of Cu slightly increases the GFA and efficiently improves the primary crystallization of α-Fe nanoparticles. The alloy with 0.3% Cu addition shows the best GFA and the fully glassy rods can be produced up to 2 mm in diameter. The saturation magnetization of the glassy sample with 0.7% Cu addition can be enhanced from 1.44 to 1.60 T after proper heat treatment due to the precipitation of α-Fe nanoparticles in the glassy matrix. The combination of large GFA and high saturation magnetization as well as low cost makes the FePCBCu alloys as a kind of promising soft magnetic materials for industrial applications.

Hot Tearing in Al-Mg-Si Alloys with Minor Additions of Cu or Mn

A study of the influence of minor additions of copper or manganese on hot tear susceptibility in Al-Mg-Si alloys has been conducted. Testing was carried out using a laboratory scale hot tearing rig and the results were validated using an analysis of cast house cracking scrap data for 6060 and 6063 extrusion billet alloys. Mn content was found to have a strong influence on hot tearing rates.

Studies on the microstructure and mechanical properties of A356 alloy with minor additions of copper and magnesium

In the present study, the effect of copper (Cu) and magnesium (Mg) addition on the microstructure and mechanical behavior of A356 alloy were investigated. Results indicate that, the minor additions of Cu in the range of 0.1–0.5% improves the mechanical properties. This is due to the partial refinement of α-Al dendrites and solid solution strengthening and precipitation hardening. Also, addition of Mg (0.3–0.7%) results in improvements in strength and hardness at the expense of ductility. This improvement is probably due to the conversion of unmodified acicular silicon (Si) to lamellar, partially rounded and even a fibrous structure.

Effects of Cu, Bi, and In on microstructure and tensile properties of Sn-Ag-X(Cu, Bi, In) solders

Effects of minor additions of Cu, Bi, and In on microstructure, melting temperature, and tensile properties of Sn-Ag-based lead-free solders were investigated. It was found that the intermetallic compounds (IMCs) Ag2In and Cu6Sn5 are formed in In- and Cu-containing solders, respectively. At low concentration, Bi dissolved in the Sn matrix and tended to precipitate pure Bi particles at the solubility limit of 4 wt pct Bi. The formation of large Ag3Sn precipitates from the solder matrix was suppressed when alloying bismuth into the Sn-Ag alloy. The Bi addition resulted in a significant linear increase of the ultimate tensile strength (UTS) of solders, which is attributed to a solid-solution hardening mechanism. Solder strengthening due to In and Cu is less pronounced and attributed to a dispersion strengthening mechanism. The additions of Cu, Bi, and In all depressed the melting temperatures of Sn-Ag-based solders; however, In is the most effective one.

Magnetic properties and microstructure of Nd–Fe–B–C magnets with Cu addition

The effect of Cu addition and annealing treatment on the microstructure and hard magnetic properties of Nd–Fe–C–B ingot-type permanent magnets was investigated. The Nd2Fe14C phase-based ingot permanent magnets were made by annealing the master alloys. The X-ray diffraction analyses showed that the microstructure consists of Nd2Fe17, Nd2Fe14C and α-Fe phases. Metallography studies showed that after annealing at 950°C for 1h the dispersed inclusions appeared in the center of the main magnetic phase grains. Minor addition of Cu to the Nd20Fe70C9.5B0.5 cast alloy is effective in enhancing the coercivity of ingot Nd–Fe–C–B-type permanent magnets. The coercivities for magnets annealed at 950°C are 630 and 880kA/m for Cu-free and 2at% Cu magnets, respectively. In order to understand the role of Cu atoms during the nucleation and grain growth stage further investigations are required.

Beneficial effects of Cu substitution on the microstructures and magnetic properties of Pr 2(FeCo) 14B/α-(FeCo) nanocomposites

We studied the phase composition, microstructures and magnetic properties of melt-spun Pr 8.5(Fe 0.8Co 0.2) 86.5− x Cu x B 5 ( x=0, 0.5, 1.0, 2.0, 3.0) nanocomposites. It was found that Cu addition suppresses the formation of Pr 2(CoFe) 17 phase and results in a two-phase mixture of α-(FeCo)/Pr 2(FeCo) 14B. Transmission electron microscopy (TEM) and energy-dispersive X-ray analysis (EDX) demonstrate that Cu strongly segregates at intergranular regions, leading to drastic decrease of the grain sizes of both 2:14:1 phase and α-(FeCo) phase. Wohlfarth remanence analysis indicates that the impact of Cu addition on the strength of exchange coupling interactions between hard and soft magnetic phases in the ribbons is determined by two opposite factors: (1) grain refinement and (2) grain isolation especially at higher Cu content. A small amount of Cu addition ( x=0–3.0) has little effect on the Curie temperature of 2:14:1 phase. The magnetic properties of B r, i H c, and ( BH) max of optimally processed Pr 8 5(Fe 0 8Co 0.2) 86.5− x Cu x B 5 ribbons initially increase with increasing Cu content from x=0 to 0.5 but all of them decrease drastically with further increasing Cu content, which can be mainly attributed to the variation of exchange coupling effect between hard and soft magnetic grains and the decrease in saturation magnetization. A combination of i H c=7.4 kOe, B r=10.9 kG and ( BH) max=20.1 MGOe has been obtained in Pr 8.5(Fe 0.8Co 0.2) 86Cu 0.5B 5 ribbon. Moreover, minor addition of Cu ( x=0.5) is effective in reducing the irreversible loss of induction ( h irr) of the studied Pr 2(FeCo) 14B/α-(FeCo) nanocomposite magnets.

Mechanism of grain size refinement of Fe3B/Nd2Fe14B nanocomposite permanent magnet by Cu addition

Minor addition of Cu to Nd4.5Fe77B18.5 melt-spun alloy is effective on reducing the grain size of the Fe3B/Nd2Fe14B nanocomposite permanent magnet produced via the crystallization route from the amorphous phase, thereby improving hard magnetic properties. Three-dimensional atom probe and transmission electron microscopy observations have shown that Cu clusters with a number density of ∼1024 m−3 is formed prior to the nucleation event of the Fe3B primary crystal. In the nucleation and growth stage of the Fe3B primary crystals, Cu clusters are in direct contact with the primary particles, suggesting that Cu clusters serve as heterogeneous nucleation sites for the Fe3B primary particles, thereby increasing the number density of the particles.