Ni Si Alloy Research Articles

Microstructure and properties of high-strength Cu–Ni–Si–(Ti) alloys

The tradeoff between the strength and the fracture elongation in the high-strength Cu–Ni–Si alloy became a hot research topic recently. Cu–Ni–Si–(Ti) alloys were fabricated in a vacuum induction melting furnace to study the effects of titanium on the microstructure and mechanical properties of Cu–Ni–Si alloys with different thermo-mechanical treatments. After homogenization at 900 °C for 4 h, hot-rolled by 80%, solution treatment at 970 °C for 2 h, cold-rolled by 50%, and finally aged at 450 °C for 180 min, the studied Cu–10Ni–Si–2Ti alloy achieved the hardness of HV 252.4, electrical conductivity of 23.6% IACS, tensile strength of 764.4 MPa, yield strength of 622.26 MPa, fracture elongation of 10.4%, and strength-elongation product of 7.95 GPa%, which are less than those of the studied Cu–10Ni–2Si alloy. The addition of Ti contributed to refining the microstructure, suppressing the decreasing trend in mechanical properties after peak hardening, and arousing a primary substructure strengthening mechanism rather than the precipitation strengthening in Cu–Ni–Si alloys. These findings provide essential understandings of the effects of the Ti on Cu–Ni–Si system alloys, and the designed Cu–Ni–Si alloys with high-strength and fracture elongation could fulfill some requirements of the electronic and electrical industry.

Simultaneously enhanced hardness and electrical conductivity in a Cu–Ni–Si alloy by addition of Cobalt

The effects of Co on the physical properties and precipitation evolution of a Cu–Ni–Si alloy are investigated via hardness and electrical conductivity testing, transmission electron microscopy and a quantitative three-dimensional atom probe. The precipitation sequence of Cu–Ni–Si alloy aging at 500 °C can be expressed as supersaturated solid solution → solute clusters → GP zones → Ni2Si phases. In the early aging stage, the formation of atomic clusters is accompanied by the occurrence of spinodal decomposition. The addition of Co accelerates the redistribution and agglomeration of solute atoms, resulting in the nucleation of (Ni, Co)2Si phases directly from the supersaturated state, which further hinders atomic cluster formation and spinodal decomposition. The Ni2Si and (Ni, Co)2Si phases, which are divided into a region II containing pure Ni2Si and the (Ni, Co)2Si phase and an unstable region I containing a small amount of Cu atoms, show the same crystal structure and orientation relationship with the matrix. During the aging process, the range of region I is gradually replaced by the core stable region II and accompanied by the growth of the total thickness of the precipitated phase. This remarkable age effect with Co addition can be attributed to the enhanced number of (Ni, Co)2Si precipitates, which simultaneously increases the strength and electrical conductivity.

The influence of process of manufacturing and heat treatment on performance and dimensional stability of the Cu—Ni—Si alloy

The possibilities of improving the properties and increasing the dimensional stability of material of the special Cu—Ni—Si alloy for the parts of electric vacuum microwave devices by the deformation and heat-treatment methods are analyzed.

Effect of Amount of Solute Atoms on Development of Heterogeneous–nano Structure in Cu–Ni–Si Alloys

Effect of Amount of Solute Atoms on Development of Heterogeneous–nano Structure in Cu–Ni–Si Alloys

Effects of Amounts of Additive Elements on Microstructure and Mechanical Properties of Heavily Cold–Rolled Cu–Ni–Si Alloys

Effects of Amounts of Additive Elements on Microstructure and Mechanical Properties of Heavily Cold–Rolled Cu–Ni–Si Alloys

Ni/Si＝2のCu–Ni–Si合金の時効析出に対するNi及びSi量の影響

Ni/Si＝2のCu–Ni–Si合金の時効析出に対するNi及びSi量の影響

Computational Screening of Efficient Additive Elements to Stabilize the Interface between Cu Matrix and Ni2Si Precipitates in Cu–Ni–Si Alloys

Computational Screening of Efficient Additive Elements to Stabilize the Interface between Cu Matrix and Ni₂Si Precipitates in Cu–Ni–Si Alloys

Characterization of Precipitated Phase in Cu–Ni–Si Alloy by Small Angle X–ray Scattering, Small Angle Neutron Scattering and Atom Probe Tomography

Characterization of Precipitated Phase in Cu–Ni–Si Alloy by Small Angle X–ray Scattering, Small Angle Neutron Scattering and Atom Probe Tomography

Effect of pre-deformation before aging on discontinuous precipitation behaviour in Cu-Ni-Si alloys

ABSTRACT The effect of deformation before aging on discontinuous precipitation in Cu–4.75wt%Ni–1.13wt%Si and Cu–6wt%Ni–1.42wt%Si alloys after solution treatment was investigated. Two kinds of deformation, one under and the other over the uniform deformation limit were implemented after solution treatment. With increasing deformation strain in both alloys, the discontinuous precipitation is accelerated and the aging time for a fully covered region by discontinuous precipitation is shortened. However, the Cu–6wt%Ni–1.42wt%Si alloy deformed under the uniform deformation limits showed an enhanced discontinuous precipitation compared to that for the alloy deformed over the uniform deformation limit. The deformation defects including dislocations and shear bands play the role of encouraging discontinuous precipitation. The shear bands formed during prior deformation beyond the necking point could provide sites for discontinuous precipitation initiation in the early stages of annealing However, shear bands tend to hinder the advance of discontinuous precipitation with further aging in the Cu–Ni–Si alloy with a high content of Ni and Si.

Cu–Ni–Si合金板の強度と導電率に及ぼす極低温高速圧延の影響

Cu–Ni–Si合金板の強度と導電率に及ぼす極低温高速圧延の影響

Effect of two-step cryorolling and aging on mechanical and electrical properties of a Cu–Cr–Ni–Si alloy for lead frames applications

Abstract High strength and high electrical conductivity Cu–Cr-based alloys are important candidate materials for preparing lead frames, railway contact wires and connects. However, high strength and high electrical conductivity are mutually exclusive in nature. To optimize the mechanical and electrical properties of a Cu–Cr–Ni–Si alloy, the two-step cryorolling and aging (CRA) was carried out in this study. Here, by the analysis of microstructure evolution, precipitation behavior, and corresponding strengthening mechanisms of the alloy at different rolling and aging conditions, we find that the yield strength and electrical conductivity for the two-step CRA sample are improved by 91.3 MPa and 4.9 %IACS (International Annealed Copper Standard) than those of the sample subjected to single-step room temperature rolling and aging (RTRA). The higher yield strength for the two-step CRA sample is mainly determined by the precipitation strengthening contributed from Ni2Si and Cr precipitates, rather than the twin boundary strengthening and dislocation strengthening. In fact, the dislocation density of the two-step CRA sample is lower than that of the single-step RTRA sample because of the faster drop rate of recovery, which weakens the effect of dislocation strengthening. The combination of the first-step aging and second-step CR process for the two-step CRA sample contributes to the formation of more precipitates from the matrix, thereby significantly increasing the precipitation strengthening and decreasing the impurity scattering in the final aging. The results provide a new preparation process and a reliable theoretical approach for optimizing the mechanical and electrical properties of the Cu–Cr alloys.

Ion beam modification of the Ni-Si solid-phase reaction: The influence of substrate damage and nitrogen impurities introduced by ion implantation

We report on the growth of thin NiSi films via the thermal reaction of Ni layers (13–35 nm) with Si(100) substrates modified by ion implantation. By introducing substrate damage or nitrogen impurities prior to the solid-phase reaction, several properties of the NiSi films can be modified: the formation temperature, texture, diffusion-limited growth rate and morphological stability. As some of the modifications to the NiSi films are rooted in the early silicide phases preceding the NiSi phase, particularly its formation temperature, special attention is devoted to the growth of the amorphous Ni-Si alloy and the crystalline δ-Ni2Si and θ-Ni2Si phases.We employed a number of experimental techniques, including in situ synchrotron x-ray diffraction (XRD), in situ Rutherford backscattering spectrometry (RBS), in situ sheet resistance measurements, ex situ ion beam channelling and ex situ pole figure measurements. We show that both the formation temperature of the NiSi films and the intensity of epitaxial and axiotaxial components of the NiSi texture can be either lowered or raised by selecting appropriate implantation conditions. Agglomeration of the NiSi films at high temperature (> 700 °C) can be slowed down, either by slowing down the mobility of the Ni and Si atoms, or by removing the morphologically destabilizing axiotaxial texture. Our results emphasize the strong interwoven nature of phase formation, texture and morphological degradation. We illustrate that the kinetics of the early stages of thin film reactions consist of more than just diffusion, i.e. nucleation can also play a crucial role.

The Nature and Compositional Peculiarities of Volcanogenic Diamonds

Abstract —We have studied volcanogenic diamonds in the context of a discussion of their genesis, including some assumption on their artificial origin. The carbon isotope composition of diamonds collected from the eruption products of Tolbachik volcano (δ13CVPDB from –22 to –29‰) is within the range of the δ13CVPDB values of natural diamonds, including those from kimberlites. The δ15NAir values of the Tolbachik diamonds, measured for the first time (–2.58 and –2.32‰), correspond to δ15NAir of volcanic gases and differ from that of atmospheric nitrogen (δ15NAir = 0‰), which may be expected in synthetic diamonds. In the studied volcanogenic diamonds, as in synthetic ones, the nitrogen impurity is unaggregated. However, such an unaggregated form of nitrogen is specific to many natural diamonds (e.g., variety II diamonds, according to Orlov’s classification). Impurity elements (Cl, F, O, S, Si, Al, Ca, and Na) are locally concentrated in volcanogenic diamonds; they are a constituent of micro- and nanoinclusions in them. The high contents of F and Cl in the studied diamonds are correlated with the composition of volcanic gases; there is no reason to expect a similar correlation in synthetic diamonds. Moreover, the studied cube-octahedral Tolbachik diamonds have a number of accessory forms, some of which are not observed in synthetic diamonds. Their surfaces are frequently covered with films composed of Mg–Fe and Ca–Mg silicates, aluminosilicates, sulfates, metal alloys, and native Al. Mineral inclusions in the studied diamonds are Mn–Ni–Si alloys and silicides varying in composition from (Mn,Ni)4Si to (Mn,Ni)5Si2, Mn5Si2, and pure Mn silicide MnSi. Summing up the obtained data, we conclude that volcanogenic diamonds form in a strongly reducing environment, in which silicides and native metals and their alloys are stable. The predominant cube-octahedral morphology of these diamonds and the unaggregated nitrogen impurity point to their short-term residence under high-temperature conditions. This makes them similar, to some extent, to synthetic diamonds. There are, however, clear differences as well. Volcanogenic diamonds are similar in compositional peculiarities, including isotope compositions, to natural diamonds that form under most unfavorable conditions, such as cuboids, balases, carbonado, and some diamonds of the eclogite paragenesis. They also resemble diamonds found in situ in harzburgite and chromitite of ophiolites. This suggests a specific mechanism of formation of both volcanogenic and ophiolitic diamonds in the oceanic lithosphere.

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.

Grain refinement and mechanical properties improvements in a high strength Cu–Ni–Si alloy during multidirectional forging

Abstract Microstructure evolutions and properties variations of a high-strength Cu–Ni–Si alloy during multidirectional forging have been systematically investigated using microstructure characterizations and properties measurements. Experiment results indicated that nano-scale grains formed in the block samples having been multidirectional forged (MDF) at room/cryogenic temperatures. With the increase of the MDF cycle, the sub-grain structure was further refined to nano-grains with tens of nanometers in diameter. The ultimate tensile strength of the cryogenic temperature multidirectional forged sample was 1057 MPa, the yield strength was 923 MPa, and the fracture elongation was 7.2%. Rather than the solid solution strengthening from solutes impeding the glide of dislocation motion and the second phase particle precipitation strengthening from the Orowan looping, the grain boundary strengthening from the Hall–Petch effects plays crucial roles in strengthening the samples having been cryogenic multidirectional forged. These findings indicated that multidirectional forging is a passport to an ultrafine-grained structure and high yield strength material for the nuclear industry.

Effect of Ni/Si mass ratio on microstructure and properties of Cu–Ni–Si alloy

Cu–Ni–Si alloys with 94 wt% Cu content and different Ni/Si mass ratios were prepared by hot pressing sintering, and then solution treatment and ageing treatment were also performed. Microstructure and phase composition along with electrical conductivity and hardness of the alloys under different treating condition was studied, and then the influence of Ni/Si mass ratio was discussed. Results showed that the as-sintered Cu–Ni–Si alloys mainly consisted of α-Cu matrix and some Ni31Si12 particles at the grain boundary as well as δ-Ni2Si phases inside the matrix. After solution treatment, most of the Ni–Si compounds decomposed, but δ-Ni2Si precipitates from the matrix after ageing treatment. With increasing Ni/Si mass ratio, the electrical conductivity and hardness of the alloys increases firstly and then decreases, while a highest combination of them achieved when the mass ratio of Ni/Si was 4:1. The effect of Ni/Si ratio on the electrical conductivity of Cu–Ni–Si alloys can be mainly ascribed to the residual content of Ni/Si in the Cu matrix after ageing treatment. When the mass ratio of Ni/Si is equal to the atomic ratio of δ-Ni2Si phase, most of the Ni and Si atoms would precipitates as δ-Ni2Si, and then the electrical conductivity reaches the highest value.

Mechanical behaviour and microstructure of heat-treated Cu–Ni–Si alloy

ABSTRACT Cu–Ni–Si alloys exhibit a good combination of strength and electrical conductivity and may be a potential candidate for utilisation in electrotechnical applications. In this work, the mechanical behaviour and its relation to the microstructure of a Cu–Ni–Si alloy, subjected to different solution heat treatment cycles, were investigated. Tensile, bend and hardness testing, in addition to Optical and Scanning Electron Microscopy, were employed, as the main analytical techniques, in the context of the present investigation. This paper is part of a Thematic Issue on Copper and its Alloys.

Microstructural characterization of cold-drawn Cu–Ni–Si alloy having high strength and high conductivity

Abstract A Cu alloy with high strength and conductivity, which are trade off characteristics, was developed using discontinuous precipitates as the hardening agent. The scanning electron microscopy and transmission electron microscopy results showed that a considerable internal strain and geometrically necessary dislocations were generated in the alloy because of discontinuous precipitation. Furthermore, nanotwins, which are rarely observed in cold-drawn Cu–Ni–Si alloys, were observed in the alloy. Since nanotwins show little effect on the electrical resistivity of Cu alloys while effectively interfering with the dislocation movement, they are one of the key factors endowing Cu alloys with the trade-off characteristics of high strength and conductivity.

Precipitation Strengthening of Cu-Ni-Si Alloy.

The work examines the effect of rhenium addition on the structure and properties of Cu–2Ni–1Si alloys. The aim of this work was to answer the question of how the addition of rhenium will affect the strengthening mechanisms of rhenium-modified, saturated, plastically deformed and aged Cu–2Ni–1Si alloys. How will this affect the crystallization process? What effect will it have on the properties? Scanning electron microscopy (SEM) and analysis of chemical composition in microareas (energy-dispersive X-ray spectroscopy, EDS), light microscopy, measurements of microhardness and conductivity of the alloys were used for the investigations. Research on chemical and phase composition were carried out with application of transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM). Modification with rhenium has caused an increase in hardness as a result of precipitation of small phases with rhenium. As the effect of supersaturation, cold plastic treatment as well as aging small phases with rhenium with a size of 200 nm to 600 nm causes both reinforcement of the alloy and makes recrystallization impossible. Re-addition also influences the stabilization of the structure.

Axial Compressibility and Thermal Equation of State of Hcp Fe–5wt% Ni–5wt% Si

Knowledge of the elastic properties and equations of state of iron and iron alloys are of fundamental interest in Earth and planetary sciences as they are the main constituents of telluric planetary cores. Here, we present results of X-ray diffraction measurements on a ternary Fe–Ni–Si alloy with 5 wt% Ni and 5 wt% Si, quasi-hydrostatically compressed at ambient temperature up to 56 GPa, and under simultaneous high pressure and high temperature conditions, up to 74 GPa and 1750 K. The established pressure dependence of the c/a axial ratio at ambient temperature and the pressure–volume–temperature (P–V–T) equation of state are compared with previous work and literature studies. Our results show that Ni addition does not affect the compressibility and axial compressibility of Fe–Si alloys at ambient temperature, but we suggest that ternary Fe–Ni–Si alloys might have a reduced thermal expansion in respect to pure Fe and binary Fe–Si alloys. In particular, once the thermal equations of state are considered together with velocity measurements, we conclude that elements other than Si and Ni have to be present in the Earth’s inner core to account for both density and seismic velocities.