Heterogeneous microstructure enables a synergy of strength, ductility and electrical conductivity in copper alloys

The article proposes a process for obtaining semi-finished products in the form of pipes made of copper alloys for electrical applications using the screw rolling method. The paper presents the results of experimental piercing and rolling of pipe samples made of Cu–0.75Cr copper alloy billets with a diameter of 45 mm. The 43.5×10.0 mm samples obtained after piercing using a two-roll screw rolling mill had exact geometrical dimensions: outer diameter deviation at the front end was up to 1 %, at the back end – up to 2.4 %; relative variation in wall thickness at the front end was 0.3÷0.5 %, at the rear end – 0.5÷1.0 %. Then pierced pipe samples were rolled using a three-roll radial-shear rolling (RSR) mini mill with a different total degree of reduction – samples were obtained with an outer diameter of 30, 25 and 18 mm. The reduction process was analyzed from the point of view of internal hole stability and deformation. In case of 30 % relative reduction of the outer diameter, rolling without a mandrel is accompanied by wall thickening. In this case, inner diameter deviations are within acceptable limits. The experiments on obtaining samples from the Cu–0.75Cr alloy by screw piercing and reduction in the RSR mill show that this scheme can be implemented in principle in industry. At the same time it is necessary to define more exactly deformation parameters (degree of deformation, choice of reduction scheme) to obtain a quality product. Various options for heat treatment (HT) of the obtained pipe samples and the effect of the HT method on electrical conductivity and hardness are considered. Samples after piercing had a conductivity of 59.3 % IACS. The maximum electrical conductivity of 76.7 % IACS was obtained on samples after quenching from a temperature of 1020 °C and aging at 450 °C for 3 h. The results of the work show the fundamental possibility of obtaining semi-finished products from copper alloys for electrical purposes using the screw rolling method.

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Anneal hardening effect in sintered copper alloys

Science of Sintering ◽

10.2298/sos0202169n ◽

2002 ◽

Vol 34 (2) ◽

pp. 169-174 ◽

Cited By ~ 8

Author(s):

Svetlana Nestorovic ◽

Boran Milicevic ◽

Desimir Markovic

Keyword(s):

Electrical Conductivity ◽

Cold Rolling ◽

Copper Alloys ◽

Recrystallization Temperature ◽

Temperature Range ◽

Hardening Effect ◽

Sintered Copper ◽

Anneal Hardening ◽

Cold Rolled

Samples of copper and copper alloys CuNi and CuNiAl were prepared by a powder metallurgical method and were then subjected to cold rolling with different degrees of deformation. Copper and copper alloys in the cold-rolled state were isochronally annealed up to the recrystallization temperature during which hardness and electrical conductivity were measured. This investigation shows that the anneal hardening effect occurs in a temperature range of 450 - 650 K, followed with an increase in hardness of alloys.

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Age-Hardening Characteristics of Cu-3Ag-0.5Zr Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.710.563 ◽

2012 ◽

Vol 710 ◽

pp. 563-568 ◽

Cited By ~ 7

Author(s):

S. Chenna Krishna ◽

K. Thomas Tharian ◽

Bhanu Pant ◽

Ravi S. Kottada

Keyword(s):

Electrical Conductivity ◽

Rocket Engine ◽

Copper Alloys ◽

Solution Treatment ◽

Aging Treatment ◽

High Strength ◽

Average Diameter ◽

Age Hardening ◽

Liquid Rocket

Among the copper alloys, the Cu-3Ag-0.5Zr alloy is one of the potential candidates for combustion chamber of liquid rocket engine because of its optimum combination of high strength with thermal conductivity. The present study is a detailed characterization of microstructure, strength, and electrical conductivity during the aging treatment. The aging cycle for Cu-3Ag-0.5Zr alloy after the solution treatment (ST) was optimized to obtain higher hardness without compromising on electrical conductivity. The precipitates responsible for strengthening in aged samples are identified as nanocrystalline Ag precipitates with an average diameter of 9.0±2.0 nm.

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Why Gold Flash Can Be Detrimental to Long-Term Reliability

Journal of Electronic Packaging ◽

10.1115/1.1646425 ◽

2004 ◽

Vol 126 (1) ◽

pp. 37-40 ◽

Cited By ~ 9

Author(s):

Jingsong Xie ◽

Ming Sun ◽

Michael Pecht ◽

David F. Barbe

Keyword(s):

Electrical Conductivity ◽

Stress Relaxation ◽

Base Metal ◽

Copper Alloys ◽

Electrical Contacts ◽

High Electrical Conductivity ◽

Electrical Failure ◽

Base Materials ◽

Insight Into

Most connectors are made from copper or copper alloys, with beryllium copper and phosphor bronze being the most common base materials due to their high electrical conductivity, low stress relaxation, and competitive cost. The most significant drawback is copper’s low resistance to corrosion, which can lead to electrical failure of connectors. For this reason, a layer of gold is often plated on the surfaces of connectors to seal off the base metal from being directly exposed to the environment. As an economical practice, gold flashing has been used to protect electrical contacts from corrosion. However, there is increasing evidence indicating that gold flashing can be detrimental in applications calling for long-term reliability. This paper provides insight into reliability issues of gold flash.

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Copper alloys with improved properties: standard ingot metallurgy vs. powder metallurgy

Metallurgical and Materials Engineering ◽

10.5937/metmateng1403207j ◽

2014 ◽

Vol 20 (3) ◽

pp. 207-216

Author(s):

Milan T. Jovanović ◽

Višeslava Rajković ◽

Ivana Cvijović-Alagić

Keyword(s):

Electrical Conductivity ◽

Powder Metallurgy ◽

Mechanical Alloying ◽

Internal Oxidation ◽

Copper Alloys ◽

Microstructural Characterization ◽

Ingot Metallurgy ◽

Vacuum Melting ◽

X Ray ◽

Scanning Electron

Three copper-based alloys: two composites reinforced with Al2O3 particles and processed through powder metallurgy (P/M) route, i.e. by internal oxidation (Cu-2.5Al composite) and by mechanical alloying (Cu-4.7Al2O3 ) and Cu-0.4Cr-0.08Zr alloy produced by ingot metallurgy (vacuum melting and casting) were the object of this investigation. Light microscope and scanning electron microscope (SEM) equipped with electron X-ray spectrometer (EDS) were used for microstructural characterization. Microhardness and electrical conductivity were also measured. Compared to composite materials, Cu-0.4Cr-0.08Zr alloy possesses highest electrical conductivity in the range from 20 to 800 ℃, whereas the lowest conductivity shows composite Cu-2.5Al processed by internal oxidation. In spite to somewhat lower electrical conductivity (probably due to inadequate density), Cu-2.5Al composite exhibits thermal stability enabling its application at much higher temperatures than materials processed by mechanical alloying or by vacuum melting and casting.

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The roles of Hf element in optimizing strength, ductility and electrical conductivity of copper alloys

Materials Science and Engineering A ◽

10.1016/j.msea.2019.04.110 ◽

2019 ◽

Vol 758 ◽

pp. 130-138 ◽

Cited By ~ 4

Author(s):

Rengeng Li ◽

Siruo Zhang ◽

Cunlei Zou ◽

Huijun Kang ◽

Tongmin Wang

Keyword(s):

Electrical Conductivity ◽

Copper Alloys

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Heterogeneous microstructure of an Al2O3 dispersion strengthened Cu by spark plasma sintering and extrusion and its effect on tensile properties and electrical conductivity

Materials Science and Engineering A ◽

10.1016/j.msea.2018.06.010 ◽

2018 ◽

Vol 730 ◽

pp. 328-335 ◽

Cited By ~ 5

Author(s):

Dengshan Zhou ◽

Xinkai Wang ◽

Ondrej Muránsky ◽

Xuerong Wang ◽

Yuehuang Xie ◽

...

Keyword(s):

Electrical Conductivity ◽

Tensile Properties ◽

Spark Plasma Sintering ◽

Heterogeneous Microstructure ◽

Plasma Sintering ◽

Spark Plasma

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Thermal Stability of Microstructure and Properties of Cu-0.5Cr-0.2Zr Alloy Subjected to ECAP and Cold Rolling

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.385.278 ◽

2018 ◽

Vol 385 ◽

pp. 278-283

Author(s):

Elena Sarkeeva ◽

Marina M. Abramova ◽

Wei Wei

Keyword(s):

Thermal Stability ◽

Electrical Conductivity ◽

Plastic Deformation ◽

Copper Alloys ◽

Physical And Mechanical Properties ◽

Initial State ◽

Microstructure And Properties ◽

Mechanical And Electrical Properties ◽

Ultrafine Grained ◽

Thermal Stability Of

Copper and copper alloys are widely used in engineering as structural materials because they have high electrical and thermal conductivity. In connection with the rapid growth of industry, special requirements are imposed on these materials, that is, they must withstand the contact mechanical loads without significant plastic deformation at elevated temperature and have stable high physical and mechanical properties. To improve the combination of strength, electrical conductivity, thermal stability, and wear resistance, low-alloyed Cu-Cr-Zr copper alloys have been subject to severe plastic deformation and aging. It the same time the analysis of the termo-stability of the formed ultrafine grained microstructure and properties is a topic task. In this work, a Cu-0.5Cr-0.2Zr (wt. %) alloy was quenched to form solid solution, equal channel angular pressed and cold rolled with following aging. The microstructure was studied, mechanical and electrical properties were also analyzed. The results showed that the ultimate strength of the Cu-Cr-Zr alloy increases with the degree of deformation at room temperature up to 630 MPa. Heat treatment at 450 ° C for 1 hour led to the precipitation of Cr and Cu5Zr particles, which increases the strength up to 660 MPa, which is 2.5 times greater than the initial state. At the same time, sufficient electrical conductivity of 70% IACS is maintained. The thermal stability of the microstructure and properties of the alloy are investigated. The reinforced alloy maintains stable the microstructure and microhardness at 450 ° C for at least 5 hours. The change in microhardness is no more than 10%. That is in agreement with the requirements of industry.

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