Evolution of the structure and mechanical properties of sheets of the Al–4.7Mg–0.32Mn–0.21Sc–0.09Zr alloy due to deformation accumulated upon rolling

The mechanical properties and microstructure of sheets of an Al–4.7Mg–0.32Mn–0.21Sc–0.09Zr alloy deformed and annealed after rolling have been investigated. The total accumulated true strain was ε_f = 3.33–5.63, and the true strain at room temperature and at 200 °C was ε_с = 0.25–2.3. The strength properties of the sheets (yield stress σ_0.2 = 495 MPa and ultimate tensile strength σ_u = 525 MPa) in the deformed state were greater than those after equal-channel angular pressing (ECAP) deformation. The mechanical properties of the deformed sheets after annealing depended on the size of subgrains inside the deformed grains bands with high-angle grain boundaries (HABs). With the increase in the annealing temperature from 150 to 300°С, the subgrain size increased from 80 to 300 nm. The relative elongation δ in the as-cast state and after annealing at 200–250°C (δ = 40–50%) was higher than that after annealing at 300–370°C (δ = 24–29%).     

Effect of roll-bonding temperature on the strength and electrical conductivity of an α-brass-clad Cu–1Cr alloy composite

Tri-layered α-brass-clad Cu–Cr-alloy composite plates were prepared by hot roll-bonding. Neither intermetallic-compound layers nor interface defects were observed at the interfaces in the as-rolled and heat-treated α-brass-clad Cu–Cr composite plates. The hardness of the as-rolled α-brass layer was greater than that of the Cu–Cr substrate, since the α-brass was strengthened by strain hardening more efficiently upon rolling. The hardness of the α-brass decreased appreciably upon annealing because of the recovery processes, whereas that of the Cu–Cr layer slightly increased after heat treatment at 450°C due to the precipitation strengthening. After the post-roll-bonding heat treatment at 450°C, the strength of the α-brass-clad Cu–Cr-alloy composite decreased with a significant increase in ductility. The electrical conductivity of the asroll-bonded α-brass clad Cu–Cr alloy composite (47–52% IACS) increased significantly (to 72–74% IACS) after the 1-h heat treatment. The strength and conductivity of the clad composite are dependent on the precipitation strengthening of Cu–Cr and recovery softening of α-brass in the course of the post-roll-bonding heat treatment.     

Cu-7Cr-0.1Ag Microcomposites Optimized for High Strength and High Condutivity

This paper (i) investigated how the microstructure, conductivity, and mechanical properties of Cu-7Cr-0.1Ag microcomposites were changed by cold drawing and subsequent heat treatment, and (ii) produced the Cu-7Cr-0.1Ag microcomposite with an optimum combination of strength and conductivity. The figure of merit Z (combining strength and conductivity) of the Cu-7Cr-0.1Ag microcomposite was larger than that of the microcomposite without silver for each heat treatment. The value of Z of the Cu-7Cr-0.1Ag microcomposite was a maximum after heat treatment for 1 h at 600 °C, indicating that this was the optimum intermediate heat treatment. The following combinations of conductivity, strength and ductility (measured as elongation to fracture) were obtained by the Cu-7Cr-0.1Ag microcomposite with η = 8: (i) 77.9% IACS (International Annealed Copper Standard), 920 MPa and 3.1%; (ii) 79.3% IACS, 880 MPa and 3.3%; and (iii) 79.9% IACS, 798 MPa and 3.5%. These values for the Cu-7Cr-0.1Ag microcomposite were larger than those of the Cu-7Cr microcomposite.     

Effect of thermomechanical treatment on microstructure and properties of Cu-Cr-Zr-Ag alloy

The effects of thermomechanical treatment on the properties and microstructure of Cu-Cr-Zr alloy and Cu-Cr-Zr-Ag alloy were investigated. Ag addition improves the mechanical properties of the alloy through solid solution strengthening and brings a little effect on the electrical conductivity of the alloy. A new Cu-Cr-Zr-Ag alloy was developed, which has an excellent combination of the tensile strength, elongation, and electrical conductivity reaching 476.09 MPa, 15.43% and 88.68% IACS respectively when subjected to the optimum thermomechanical treatment, i.e., solution-treating at 920°C for 1 h, cold drawing to 96% deformation, followed by aging at 400°C for 3 h. TEM analysis re-vealed two kinds of finely dispersed precipitates of Cr and Cu4Zr. It is very important to use the mechanisms of solid solution strengthening, work hardening effect as well as precipitate pinning effect of dislocations to improve tensile strength of the alloy without adversely affecting its electrical conductivity.     

加工工艺对高性能铜合金组织和性能的影响

在真空感应炉熔炼得到Cu-0.2Cr-0.1Ag合金,研究了该合金在不同加工条件下的组织、强度和导电性变化.研究表明,通过固溶强化、时效强化和形变强化等手段的配合,可以获得高强度、高导电性的Cu-0.2Cr-0.1Ag合金.固溶、时效处理后的合金导电率达91%IACS,伸长率为37.4%.在固溶后加入冷变形,然后再时效,可以使强度提高84 MPa,而导电率不发生变化,再继续冷变形可以使强度提高到556 MPa.     

Microstructure and Precipitate's Characterization of the Cu-Ni-Si-P Alloy

Microstructure of the Cu-Ni-Si-P alloy was investigated by transmission electron microscopy (TEM). The alloy had 551 MPa tensile strength, 226 HV hardness, and 36% IACS electrical conductivity after 80% cold rolling and aging at 450 °C for 2 h. Under the same aging conditions, but without the cold rolling, the strength, hardness, and electrical conductivity were 379 MPa, 216 HV, and 32% IACS, respectively. The precipitates identified by TEM characterization were δ-Ni₂Si. Some semi-coherent spherical precipitates with a typical coffee bean contrast were found after aging for 48 h at 450 °C. The average diameter of the observed semi-coherent precipitates is about 5 nm. The morphology of the fracture surface was observed by scanning electron microscopy. All samples showed typical ductile fracture. The addition of P refined the grain size and increased the nucleation rate of the precipitates. The precipitated phase coarsening was inhibited by the small additions of P. After aging, the Cu-Ni-Si-P alloy can gain excellent mechanical properties with 804 MPa strength and 49% IACS conductivity. This study aimed to optimize processing conditions of the Cu-Ni-Si-P alloys.     

In situ TiB2/Cu composites fabricated by spray deposition using solid−liquid and liquid−liquid reactions

In situ TiB₂/Cu composites were fabricated by both solid−liquid (S−L) and liquid−liquid (L−L) reactive spray deposition in combination with cold rolling and annealing. The microstructure and properties of the fabricated TiB₂/Cu composites were investigated. The results show that the reactive mode and rolling treatment are the main factors affecting the microstructure and properties of the TiB₂/Cu composite. The in situ reaction in the L−L reaction can be carried out more completely. By controlling the rolling and annealing process, the relative density and the properties of the as-deposited composites are optimized. The comprehensive performance of the deformed TiB₂/Cu composite prepared by L−L reactive spray deposition (401 MPa and 83.5% IACS) is better than that by S−L reactive spray deposition (520 MPa and 20.2% IACS).     

大变形Ag-10Cu原位纤维复合材料的应变强化效应

利用热挤压加冷拉拔制备Ag-10Cu原位纤维复合材料。Ag-10Cu合金铸态及挤压态结构由Ag基体、(Ag+Cu)共晶体和Cu沉淀组成。经大变形后变成Ag基体加Cu纤维的两相组织,合金中的Cu相转变成Cu纤维,其尺寸d随拉拔应变η呈幂指数关系变化,且可拟合为d=d0exp(-0.144η),其中d0是与Cu沉淀初始尺寸有关的系数。讨论了材料强度的两个阶段变化及其强化机制。所制备的材料可以达到抗拉强度接近1GPa及电导率大于60%IACS的较优性能组合。还讨论了中间热处理的影响。     

Microstructure and properties of Cu−2Cr−1Nb alloy fabricated by spark plasma sintering

Cu?2Cr?1Nb alloy was fabricated by spark plasma sintering (SPS) using close coupled argon-atomized alloy powder as the raw material. The optimal SPS parameters obtained using the L₉(3⁴) orthogonal test were 950 °C, 50 MPa and 15 min, and the relative density of the as-sintered alloy was 99.8%. The rapid densification of SPS effectively inhibited the growth of the Cr₂Nb phase, and the atomized powder microstructure was maintained in the grains of the alloy matrix. Uniformly distributed multi-scale Cr₂Nb phases with grain sizes of 0.10?0.40 μm and 20?100 nm and fine grains of alloy matrix with an average size of 3.79 μm were obtained. After heat treatment at 500 °C for 2 h, the room temperature tensile strength, electrical conductivity, and thermal conductivity of the sintered Cu?2Cr?1Nb alloy were 332 MPa, 86.7% (IACS), and 323.1 W/(m·K), respectively, and the high temperature tensile strength (700 °C) was 76 MPa.     

Effect of elevated-temperature annealing on microstructureand properties of Cu−0.15Zr alloy

Cu−0.15Zr (wt.%) alloy with uniform and fine microstructure was fabricated by rapid solidification followed by hot forging. Evolution of microstructure, mechanical properties and electrical conductivity of the alloy during elevated-temperature annealing were investigated. The alloy exhibits good thermal stability, and its strength decreases slightly even after annealing at 700 °C for 2 h. The nano-sized Cu₅Zr precipitates show significant pinning effect on dislocation moving, which is the main reason for the high strength of the alloy. Additionally, the large-size Cu₅Zr precipitates play a major role in retarding grain growth by pinning the grain boundaries during annealing. After annealing at 700 °C for 2 h, the electrical conductivity of samples reaches the peak value of 88% (IACS), which is attributed to the decrease of vacancy defects, dislocations, grain boundaries and Zr solutes.     

Corrosion behavior of novel Cu–Ni–Al–Si alloy with super-high strength in 3.5% NaCl solution

A novel Cu–6.5Ni–1Al–1Si–0.15Mg–0.15Ce alloy with super-high strength was designed and its corrosion behavior in 3.5% NaCl solution at 25 °C was investigated by the means of SEM observation, TEM observation and XPS analysis. The alloy after solution treatment, 80% cold rolling and aging at 450 °C for 1 h had the best comprehensive properties with hardness of HV 314, electrical conductivity of 19.4% IACS, tensile strength of 1017 MPa, and average annual corrosion rate of 0.028 mm/a. The oxides and chloride products formed at first, followed by the formation of dyroxides products. The alloy showed super-high strength, good electrical conductivity and corrosion resistant because Ni₂Si hindered the precipitation of large NiAl at the grain boundary and the denickelefication of the alloy.     

合金元素及中间退火对Cu-Cr系形变原位复合材料组织和性能的影响

采用冷拔结合中间退火工艺制备出Cu-13%Cr-0.24%Zr、Cu-15%Cr-0.24%Zr和Cu-15%Cr形变原位复合线材。研究了Cr含量、Zr元素、中间退火温度及次数对线材极限抗拉强度及导电性能的影响。结果表明:Zr元素可显著提高材料的强度,且对其导电性能影响不大;提高Cr元素含量,对材料的强度有一定贡献,但效果不明显。增加中间退火次数和提高中间退火温度都会使材料的极限抗拉强度降低,导电率升高。本实验中,通过两次500oC中间退火工艺制备的Cu-15%Cr-0.24%Zr线材获得较为优异的综合性能,抗拉强度达到1056MPa,导电率达到73%IACS。     

变形方式对Cu-8.3Fe-1Ag形变原位复合材料组织性能的影响

分别采用冷拉拔和冷轧变形并结合中间退火工艺,制备了丝状和带状形变Cu-8.3Fe-1Ag原位复合材料。用SEM、精密万能试验机、显微硬度计和电阻测量仪对两种变形方式下试样的微观组织、力学性能和导电性能进行了比较研究。微观组织观察表明:冷拉拔和冷轧变形试样的横截面组织形貌有显著差异,前者为基体上分布着弯曲、扭折、交叠的蠕虫状相,后者为基体上定向排列着与冷轧方向平行的平直颗粒相。力学性能和导电率测试结果表明:相同应变量下,冷拉拔变形的抗拉强度、硬度均高于冷轧变形,但二者的导电率几乎相同。应变量达到6.70时,二者的抗拉强度/硬度/导电率分别达到838 MPa/149 HV/58%IACS和924 MPa/160 HV/58%IACS。     

Microstructural characterization and mechanical properties of friction surfaced AA2024−Ag composites

The effects of Ag on the microstructure, mechanical properties, and electrical conductivity of AA2024 aluminum alloy coating were investigated. It was fabricated by friction surfacing as an additive manufacturing process. To carry out this investigation, Ag was added by 5.3, 10.6, and 16.0 wt.% to an AA2024 consumable rod by inserting holes in it. It was found that due to the strengthening by solid solution and the formation of precipitates and intermetallic containing Ag, the driving force for grain growth is reduced and consequently the grain size of the coating is decreased. After artificial aging heat treatment, the electrical conductivities of the coatings containing 0 and 16.0 wt.% Ag are increased by 4.15% (IACS) and decreased by 2.15% (IACS), respectively. While considering a linear relationship, it can be proposed that for a 1 wt.% Ag increase, the strength and hardness of the coating will be increased by 1.8% and 1.0%, respectively. It was established that the effect of Al₆(Cu,Ag)Mg₄ precipitate formation on strengthening is greater than that of Ag-rich intermetallic.     

Single-aging characteristics of 7055 aluminum alloy

The microstructures and properties of 7055 aluminum alloy were studied at different single-aging for up to 48 h using hardness test, tensile test, electrical conductivity measurement, XRD and TEM microstructure analysis. The results show that at the early stage of aging, the hardness and strength of the alloy increase rapidly, the peak hardness and strength are approached after 120 ℃ aging for 4 h, then maintained at a high level for a long time. The suitable single-aging treatment of 7055 alloy is 480 ℃, 1 h solution treatment and water quenching, then aging at 120 ℃ for 24 h. Under those condition, the tensile strength, yield strength, elongation and electrical conductivity of the studied alloy are 513 MPa, 462 MPa, 9.5% and 29%（IACS）, respectively. During aging, the solid solution decomposes and precipitation occurs. At the early aging stage of 120 ℃, GP zones form and then grow up gradually with increasing ageing time. η′ phase forms after ageing for 4 h and η phase starts to occur after 24 h aging.     

时效处理对形变Cu-10Fe-3Ag组织及性能的影响

研究时效处理对形变Cu-10Fe-3Ag复合材料组织和性能的影响,分析合金元素Ag在时效过程中的行为规律和作用机制。结果表明,Ag能够促进γ-Fe在Cu基体中的时效析出,同时也降低了Fe纤维的热稳定性;随着时效温度的升高,形变Cu-10Fe-3Ag复合材料的硬度和导电率都是先增加后降低,在475℃时效6h,导电率达到58.4%IACS。合金的断口均为韧性断裂,随着时效温度的升高,韧窝有变小的趋势,合金的塑性变好。     

Sintering behavior of W–30Cu composite powder prepared by electroless plating

Powder metallurgy technique was employed to prepare W–30 wt.% Cu composite through a chemical procedure. This includes powder pre-treatment followed by deposition of electroless Cu plating on the surface of the pre-treated W powder. The composite powder and W–30Cu composite were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Cold compaction was carried out under pressures ranging from 200 MPa to 600 MPa while sintering at 850 °C, 1000 °C and 1200 °C. The relative density, hardness, compressive strength, and electrical conductivity of the sintered samples were investigated. The results show that the relative sintered density of the titled composites increased with the sintering temperature. However, in solid sintering, the relative density increased with pressure. At 1200 °C and 400 MPa, the liquid-sintered specimen exhibited optimum performance, with the relative density reaching as high as 95.04% and superior electrical conductivity of IACS 53.24%, which doubles the national average of 26.77%. The FE-SEM microstructure evaluation of the sintered compacts showed homogenous dispersion of Cu and W and a Cu network all over the structure.     

Effect of rolling and annealing processes on the hardness and electrical conductivity values of Cu-13.5%Mn-4%Ni alloy

It was found that the dendritic microstructure of an as-cast alloy was changed to an almost equiaxed alloy after 480 min of annealing at 700 °C. The electrical conductivity of as-cast and hot rolled samples increased from 27.36 and 30.51% IACS to 30.67 and 32.1% IACS after 480 min of annealing at 700 °C. The dendritic microstructure and the electrical conductivity values of an as-cast alloy annealed for 60 min remained almost unchanged when the annealing temperature was increased to 800 °C. The hardness values of the samples that were hot rolled and annealed for 60 min were higher than those of the as-cast samples for all annealing temperatures. The electrical conductivity values of the hot rolled and as-cast samples were almost the same after annealing at 800 °C for 60 min. It was shown that after 20% cold work, the electrical conductivity value of the as-cast sample decreased from 30.5% IACS to 22.6% IACS. The electrical conductivity values of the samples were not significantly changed when the cold work was increased from 20% to 60%. The electrical conductivity values of the 20%, 40% and 60% cold worked samples increased from 22.62, 24.69 and 26.63 to 27.14,28.36 and 30.55% IACS, respectively, after 30 min annealing at 400 °C.     

Effect of Zr and Sc on mechanical properties and electrical conductivities of Al wires

In order to obtain the Al wires with good mechanical properties and high electrical conductivities, conductive wires of Al–0.16Zr, Al–0.16Sc, Al–0.12Sc–0.04Zr (mass fraction, %) and pure Al (99.996%) were produced with the diameter of 9.5 mm by continuous rheo-extrusion technology, and the extruded materials were heat treated and analyzed. The results show that the separate additions of 0.16% Sc and 0.16% Zr to pure Al improve the ultimate tensile strength but reduce the electrical conductivity, and the similar trend is found in the Al–0.12Sc–0.04Zr alloy. After the subsequent heat treatment, the wire with the optimum comprehensive properties is Al–0.12Sc–0.04Zr alloy, of which the ultimate tensile strength and electrical conductivity reach 160 MPa and 64.03% (IACS), respectively.     

Microstructure and properties of Al2O3 dispersion-strengthened copper fabricated by reactive synthesis process

Al2O3 dispersion-strengthened copper alloy was prepared by reactive synthesis and spark plasma sintering(SPS) process. Studies show that nano-sized c-Al2O3 particles with 27.4 nm mean size and 50-nm interval are homogeneously distributed in copper matrix. The density of SPS alloy is about 99 %, meanwhile, the electrical conductivity of sintered alloy is 72 % IACS and the Rockwell hardness can reach to HRB 91.