Electrical annealing of severely deformed copper: microstructure and hardness

Commercial pure copper sheets were severely deformed after primary annealing to a strain magnitude of 2.32 through constrained groove pressing. After induction of an electrical current, the sheets were heated for 0.5, 1, 2, or 3 s up to maximum temperatures of 150, 200, 250, or 300℃. To compare the annealing process in the current-carrying system with that in the current-free system, four other samples were heated to 300℃ at holding times of 60, 90, 120, or 150 s in a salt bath. The microstructural evolution and hardness values of the samples were then investigated. The results generally indicated that induction of an electrical current could accelerate the recrystallization process by decreasing the thermodynamic barriers for nucleation. In other words, the current effect, in addition to the thermal effect, enhanced the diffusion rate and dislocation climb velocity. During the primary stages of recrystallization, the grown nuclei of electrically annealed samples showed greater numbers and a more homogeneous distribution than those of the samples annealed in the salt bath. In the fully recrystallized condition, the grain size of electrically annealed samples was smaller than that of conventionally annealed samples. The hardness values and metallographic images obtained indicate that, unlike the conventional annealing process, which promotes restoration phenomena with increasing heating time, the electrical annealing process does not necessarily promote these phenomena. This difference is hypothesized to stem from conflicts between thermal and athermal effects during recrystallization.

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 ℃ 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.

Influence of annealing treatment on properties and microstructures of alumina dispersion strengthened copper alloy

Alumina dispersion strengthened copper（ADSC） alloy was produced by internal oxidation. The hardness, ultimate tensile strength and electrical conductivity measurements and microstructure observation on the produced 0.12%ADSC （0.24% Al2O3, mass fraction） and 0.25%ADSC （0.50% Al2O3） subjected to different annealing treatments were conducted. The results show that the microstructure of the produced ADSC is characterized by an uniform distribution of nano-Al2O3 particles in Cu-matrix; the particles range in size from 20 to 50 nm with an interparticle spacing of 30100 nm. The produced 0.12%ADSC can maintain more than 87% hardness retention after 900 ℃, 1 h annealing treatment; the recrystallization can be largely retarded and is not fully completed even after annealing at 1 000 ℃ for 1 h, followed by cold deformation of 84%; local grain growth can be observed after 1 050 ℃, 1 h annealing treatment. The results also show that increasing either the alumina content or cold deformation degree increases the hardness of the produced ADSC.

Microstructure and properties of copper matrix composites reinforced by nano-SiC and nano-Al_2O_3 particles

Copper/silicon carbide composites （Cu/SiC） and copper/alumina composites （Cu/Al2O3） were fabricated by the powder metallurgy method. The influence of reinforcement particles contents on the relevant properties of the composites and the microstructure of Cu/SiC and Cu/Al2O3 composites were studied. The reinforcement effects of nano-SiC and nano-Al2O3 particles were compared. The experimental results show that with the increase of the amount of nano-SiC and nano-Al2O3 particles, the density of the both composites decreases, the resistivity increases, whereas the hardness increases firstly and then drops. The softening temperatures of the composites are above 700℃ which is far higher than that of the pure copper, leading to the improvement of the thermal stability of the composites at high temperatures. Considering all factors, the reinforcement effects of nano-SiC are better than those of nano-Al2O3 when their contents are the same in the copper matrix.

Investigation of Cast Copper Structure

In this paper,the results of exploration macrostructure and microstructure of continuous cast copper bars are shown. Quantitative parameters of copper cast bars depending on the speed of continuous casting are rated. It is fixed that independent of speed of casting the macrocrystalline columnar structure consisting of four zones is formed. By means of raster electron microscopy,the microstructure of cast copper is studied. It is determined that the accumulations of eutectic Cu-Cu2O in the form of lines and gas pores by size from 2 to 35 microns at the boundaries grain are observed. With the use of the transmission electron microscope,specific dislocation configuration on cast copper sub-boundary grains is determined. It indicates to high-temperature strain of cupper in the course of cast bar solidification. The important finding can be used for the design technology of copper continuous casting and plastic working of cast bars.

IMPROVING THE MECHANICAL PROPERTIES OF COPPER ALLOYS BY THERMO-MECHANICAL PROCESSING

Systematic physical simulation of thermo-mechanical processing routes has been ap-plied on a Gleeble 1500 simulator to four copper alloys (mass %) Cu-0.57Co-0.32Si,Cu-0.55Cr-0.065P, Cu-0.22Zr-0.035Si and Cu-1.01Ni-0.43Si aimed at clarifying theinfluences of processing conditions on their final properties, strength and electricalconductivity. Flow curves were determined over wide temperature and strain rateranges. Hardness was used as a measure of the strength level achieved. High hard-ness was obtained as using equal amounts (strains 0.5) of cold deformation beforeand after the precipitation annealing stage. The maximum values achieved for theCu-Co-Si, Cu-Cr-P, Cu-Zr-Si and Cu-Ni-Si alloys were 190, 165, 178 and 193 HV5,respectively. A thermo-mechanical schedule involving the hot deformation-ageing-colddeformation stages showed even better results for the Cu-Zr-Si alloy. Consequently,the processing routes were designed based on simulation test results and wires of 5 and2mm in diameters have been successfully processed in the industrial scale.

Effects of normal stress, surface roughness, and initial grain size on the microstructure of copper subjected to platen friction sliding deformation

The effects of applied normal stress, surface roughness, and initial grain size on the microstructure of pure Cu developed during platen friction sliding deformation （PFSD） processing were investigated. In each case, the deformation microstructure was characterized and the hardness of the treated surface layer was measured to evaluate its strength. The results indicated that the thickness of the deformed layer and the hardness at any depth increased with increasing normal stress. A smaller steel platen surface roughness resulted in less microstruc- tural refinement, whereas the microstructural refinement was enhanced by decreasing the surface roughness of the Cu sample. In the case of a very large initial grain size （d 〉 10 mm）, a sharper transition from fine-grain microstructure to undeformed material was obtained in the treated surface layer after PFSD processing.

Wear Evaluation of Copper-Nickel-Aluminum Alloys under Extreme Conditions

Cu-Ni-Al alloys at different concentrations were obtained using a high frequency induction melting unit, keeping a balance in the nominal compositions. Light alloys are important to be used in industrial applications. Aluminum additions result in a positive hardness increment of the ternary alloys in comparison with the binary Cu-Ni alloys. Generalized wear mechanisms of the alloys with low aluminum content are basically type abrasive, while samples with 5 and 10 at.% Al present an oxidative-adhesive wear mechanism. Wear results have indicated that aluminum addition affects positively the wear resistance, mainly in samples with high aluminum content product of the creation during the test of different oxides corresponding to the elements present in the alloys.

Exciting News from Indentations onto Silicon, Copper, and Tungsten

Indentations onto crystalline silicon and copper with various indenter geometries, loading forces at room temperature belong to the widest interests in the field, because of the physical detection of structural phase transitions. By using the mathematically deduced FNh3/2 relation for conical and pyramidal indentations we have a toolbox for deciding between faked and experimental loading curves. Four printed silicon indentation loading curves (labelled with 292 K, 260 K, 240 K and 210 K) proved to be faked and not experimental. This is problematic for the AI (artificial intelligence) that will probably not be able to sort faked data out by itself but must be told to do so. High risks arise, when published faked indentation reports remain unidentified and unreported for the mechanics engineers by reading, or via AI. For example, when AI recommends a faked quality such as “no phase changes” of a technical material that is therefore used, it might break down due to an actually present low force, low transition energy phase-change. This paper thus installed a tool box for the distinction of experimental and faked loading curves of indentations. We found experimental and faked loading curves of the same research group with overall 14 authoring co-workers in three publications where valid and faked ones were next to each other and I can thus only report on the experimental ones. The comparison of Si and Cu with W at 20-fold higher physical hardness shows its enormous influence to the energies of phase transition and of their transition energies. Thus, the commonly preferred ISO14577-ASTM hardness values HISO (these violate the energy law and are simulated!) leads to almost blind characterization and use of mechanically stressed technical materials (e.g. airplanes, windmills, bridges, etc). The reasons are carefully detected and reported to disprove that the coincidence or very close coincidence of all of the published loading curves from 150 K to 298 K are constructed but not experimental. A tool-box for distinction of experimental from faked indentation loading curves (simulations must be indicated) is established in view of protecting the AI from faked data, which it might not be able by itself to sort them out, so that technical materials with wrongly attributed mechanical properties might lead to catastrophic accidents such as all of us know of. There is also the risk that false theories might lead to discourage the design of important research projects or for not getting them granted. This might for example hamper or ill-fame new low temperature indentation projects. The various hints for identifying faked claims are thus presented in great detail. The low-temperature instrumental indentations onto silicon have been faked in two consecutive publications and their reporting in the third one, so that these are not available for the calculation of activation energies. Conversely, the same research group published an indentation loading curve of copper as taken at 150 K that could be tested for its validity with the therefore created tools of validity tests. The physical algebraic calculations provided the epochal detection of two highly exothermic phase transitions of copper that created two polymorphs with negative standard energy content. This is world-wide the second case and the first one far above the 77 K of liquid nitrogen. Its existence poses completely new thoughts for physics chemistry and perhaps techniques but all of them are open and unprepared for our comprehension. The first chemical reactions might be in-situ photolysis and the phase transitions can be calculated from experimental curves. But several further reported low temperature indentation loading curves of silicon were tested for their experimental reality. And the results are compared to new analyses with genuine room temperature results. A lot is to be learned from the differences at room and low temperature.

The Microstructure and Properties of Copper with Ceria Nanoparticles Addition

Copper-based composites strengthened by ceria nanoparticles were processed by conventional powder metallurgy: mixing (30 min and 46 rpm), compaction (cold, uniaxial, 1080 MPa for 10 s) and sintering (800°C for 6 h in vacuum atmosphere of 10−5 torr). It was studied the microstructure (optical microscopy, scanning electron microscopy), X-ray diffraction with Rietveld refinement and some properties (electrical conductivity, Vickers hardness and fracture analysis) of the compositions 92 wt% Cu - 8 wt% CeO2 and 80 wt% Cu - 20 wt% CeO2. The results showed uniform phase distribution, low porosity and ceria disperse inside copper grain. In despite of properties, the composites had electrical conductivity of 38% IACS and 15% IACS and hardness of 69 and 88 HV5, respectively. The results of 92 wt% Cu - 8 wt% CeO2 composites were promising, and they are in according with actual literature.

Electroless copper-phosphorus coatings with the addition of silicon carbide (SiC) particles

Cu-P-silicon carbide （SiC） composite coatings were deposited by means of electroless plating.The effects of pH values,temperature,and different concentrations of sodium hypophosphite （NaH2PO2·H2O）,nickel sulfate （NiSO4·6H2O）,sodium citrate （C6H5Na3O7·2H2O） and SiC on the deposition rate and coating compositions were evaluated,and the bath formulation for Cu-P-SiC composite coatings was optimised.The coating compositions were determined using energy-dispersive X-ray analysis （EDX）.The corresponding optimal operating parameters for depositing Cu-P-SiC are as follows：pH 9;temperature,90oC;NaH2PO2·H2O concentration,125 g/L;NiSO4·6H2O concentration,3.125 g/L;SiC concentration,5 g/L;and C6H5Na3O7·2H2O concentration,50 g/L.The surface morphology of the coatings analysed by scanning electron microscopy （SEM） shows that Cu particles are uniformly distributed.The hardness and wear resistance of Cu-P composite coatings are improved with the addition of SiC particles and increase with the increase of SiC content.

多孔铜箔对硬碳负极电化学性能的影响

负极集流体是锂离子电池的重要组成部分,直接决定电池的内阻,影响电池的倍率和循环稳定性。以常规铜箔和多孔铜箔作为集流体制备锂离子电池,通过SEM、极片电阻、接触角和恒流充放电等测试,研究铜箔带孔对电池容量、倍率性能及循环性能的影响。与常规铜箔相比,以多孔铜箔作为集流体制备的极片具有更低的电阻率和更佳的电解液浸润效果,制备的扣式半电池以0.1 C在0.001~2.500 V循环3次进行化成后,首次充放电比容量分别提高了149.50 mAh/g和207.03 mAh/g;在10.0 C倍率下的平均放电比容量达127.21 mAh/g,较常规铜箔制备的电池提升了46.28%;以1.0 C在0.001~2.500 V循环200次后,电池的容量保持率达52.85%,材料的倍率性能和循环稳定性得到提升。

石墨烯增强铜复合材料摩擦性能研究

通过原位合成石墨烯结合粉末烧结法制备了石墨烯增强铜复合材料,然后在空气环境中研究石墨烯增强铜复合材料的摩擦性能。实验选用直径为6 mm的WC磨球与复合材料组成摩擦副,利用摩擦磨损试验机对材料进行摩擦磨损测试。采用SEM、EBSD、EDS和三维轮廓形貌仪等相关检测设备对复合材料的微观组织结构以及磨损的表面形貌结构进行分析表征。结果表明,相比于纯铜材料,石墨烯增强铜复合材料具有更低的摩擦系数,这主要归功于复合材料较高的硬度以及石墨烯的自润滑效应。最后结合复合材料的磨损形貌给出了相关的磨损机制。

镀铜石墨对铜基金属结合剂砂轮性能的影响

文章旨在研究镀铜石墨对铜基金属结合剂砂轮性能的影响,将镀铜石墨和普通石墨按照研究方案设计的比例均匀混合,采用热压烧结的方法制成胎体试条,且在混合粉末中添加超硬磨料制成金属结合剂超硬材料砂轮,利用硬度计、电子万能试验机、扫描电镜、划片机等设备,分别测试和研究了金属结合剂胎体硬度、抗折强度、断口形貌以及金属结合剂超硬材料砂轮切割性能。通过对以上结果的分析,揭示了镀铜石墨含量的不同对金属结合剂胎体及超硬材料砂轮性能的影响规律。试验数据表明镀铜石墨的添加有利于提高金属结合剂胎体的硬度和抗折强度,最高可分别提升8.4%和25.5%;另一方面增加了超硬材料砂轮的耐磨性,相同试验条件下磨耗降低了60%。

西藏某细粒难选型铜矿浮选试验研究

针对西藏某细粒难选铜矿进行了浮选试验研究,通过磨矿细度试验、浮选浓度试验、捕收剂种类和用量试验、活化剂用量以及强化回收伴生元素试验,优化了浮选工艺参数和药剂制度。在最佳工艺参数和药剂制度条件下,闭路试验可以获得精矿Cu品位28.33%、Au品位12.60 g/t、Ag品位564.32 g/t、Mo品位0.62%,Cu回收率91.31%、Au回收率80.59%、Ag回收率66.69%、Mo回收率69.68%的理想试验指标。

整平剂对酸性电镀硬铜的影响

研究了噻唑啉基二硫代丙烷磺酸钠（SH110）、十六烷基三甲基溴化铵（CTMAB）、聚乙烯亚胺烷基盐（PN）以及四氢噻唑硫酮（H1）4种整平剂对酸性电镀铜层表面形貌和显微硬度的影响。基础镀液组成为：CuSO4·5H2O 220g／L，H2SO4 55g／L，Cl^- 60mg／L，聚二硫二丙烷磺酸钠（SPS）3mg／L，聚乙二醇（PEG6000）100mg／L。在一定范围内，整平剂的质量浓度越高，镀层表面越光滑、平整，显微硬度越高。选择2g／LH1作为整平剂时，所得镀层的显微硬度可长时间（14d以上）满足电子雕刻的要求（180～220HV）。H1与其他3种整平剂之间的协同作用的强度顺序为：H1＋SH110〉H1＋CTMAB〉H1＋PN。

电沉积铜的工艺参数对镀层硬度及电阻率的影响

通过改变镀铜工艺中的阴极电流密度参数 ,测定所获得镀铜层的硬度及电阻率 ,发现阴极电流密度与镀铜层的硬度及电阻率之间的变化趋势 ,硬度与电阻率的时间效应。