The article describes the influence of anomalous values and local variability on the structure of variability and the estimation of deposit parameters. The research was carried out using statistical and geostatistical methods based on the Pb accumulation index in the shale series in part of the Cu-Ag ore deposit, LGCD (Lubin-Głogów Copper District). The authors recommend the use of a geostatistical tool, the so-called semivariogram cloud to determine the anomalous values. Anomalous values determined by the geostatistical method and removed from the dataset have resulted in a significant reduction of the relative variability of data, which is still very large in the case of the analyzed parameter or parameters with similar statistical features such as extreme variability and strongly asymmetric distribution. Calculations of the resources of this element can be treated only as estimates and formally classified to category D. The hypothetical assumption of the absence of sampling errors, resulting in a decrease in the magnitude of local variation, leads to a certain reduction of the median error of resource estimates. However, they are still high (> 35%). This is due to the large natural variability of the accumulation index of Pb on the local observation scale. The current method for collecting samples from mine workings of the Cu-Ag deposits in the Lubin-Głogów Copper District (LGCD), aimed at the proper assessment of copper resources, the Cu content, and at estimating the quality of copper output, makes it impossible to achieve an accuracy of estimates of Pb resources similar to that obtained for the main metal. Theoretically, this effect can be achieved by a strong concentration of the sample collection points and thanks to a multiple increase in the samples weight; this, however, is unrealistic for both economic and organizational reasons. It is therefore to be expected that the assessment of Pb resources and other accompanying elements of similar statistical features (e.g. As), located in parts of the deposit where mining activities are to be carried out, will be subject to significant errors.
The paper proposes a method for copper sheet oxidation by using a laser beam. The thickness of the oxide layer increases with temperature growth; therefore, the proper parameters of the experiment such as pulse power, frequency and the speed of the beam were adjusted. High power diode laser was used in the investigations. The topography of the oxidised copper sheets was determined using atomic force microscopy (AFM) and scanning electron microscopy with EDS analyses. Optical parameters of the deposited layer were characterised by spectrophotometry. Both roughness and thickness of the investigated samples were measured using the confocal laser scanning microscope. The technological recommendations for the laser micro-machining technology to obtain copper sheet oxidation by using the high power laser beam were selected.
Eutectic copper oxides (Cu2O) crystallize during the copper solidification process in the ETP grade copper which leads to high oxygen concentrations in interdendritic spaces. It has been experimentally found that they can be regular or elongated, and their size reaches several micrometres. During the multi-cage hot rolling process, homogenization of the oxide distribution in the entire volume of the wire rod occurs. This process is carried out in the soft copper matrix. Throughout the drawing process the fragmentation of oxides transpires along with changes in the shape from angular to more oval in a degree depending on the size of the deformation (wire diameter). Microcracks, fissures and local stress fields in the reinforced copper matrix arise around the oxide particles. The article presents the results of research on the evolution of copper oxides in ingots, wire rods and wires. The results of investigations of the wires properties and the limitations of the drawing process, especially of microwires, are presented.
Secondary or multiple remelted alloys are common materials used in foundries. For secondary (recycled) Al-Si-Cu alloys, the major problem is the increased iron presence. Iron is the most common impurity and with presence of other elements in alloy creates the intermetallic compounds, which may negatively affect the structure. The paper deals with effect of multiple remelting on the microstructure of the AlS9iCu3 alloy with increased iron content to about 1.4 wt. %. The evaluation of the microstructure is focused on the morphology of iron-base intermetallic phases in caste state, after the heat treatment (T5) and after natural aging. The occurrence of the sludge phases was also observed. From the obtained results can be concluded that the multiple remelting leads to change of chemical composition, changes in the final microstructure and also increases sludge phases formation. The use of heat treatment T5 led to a positive change of microstructure, while the effect of natural aging is beneficial only to the 3rd remelting.
In this study, copper nanoparticles and nanofluids were synthesized by electrical explosion of wire (EEW) in liquid media such as water, ethanol, and acetone. The effect of the different conditions on the properties of the as-synthesized Cu powders and nanofluids were investigated. X-ray diffraction (XRD) analysis was employed to measure the phase of the as-synthesized powder. Only pure Cu phase appeared in case of acetone condition, but CuO and CuO2 phases could be observed in the others. The EEWed particle size was broadened from under 50 to 100 nm. The results showed that acetone was the best condition for achieving smaller particles, preventing the oxidation of the Cu particles and good stability of the nanofluids.
The presented access the influence of Mn content (0-0.94 wt.%) on the course of the cooling curves, phase transformation, macrostructure, and microstructure of Al-Cu alloys for three series: initial (Series I), with the addition of an AlTi master (Series II), and modified with AlTi5B1 (Series III). The maximum degree of undercooling ΔT was determined based on the cooling curves. The surface density of the grains (NA) was determined and associated with the inverse of solidification interval 1/ΔTk. Titanium (contained in the charge materials as well as the modifier) has a significant effect on the grinding of the primary grains in the tested alloys. A DSC thermal analysis allowed for the determination of phase transition temperatures under conditions close to equilibrium. For series II and III, the number of grains decreases above 0.2 wt.% Mn with a simultaneous increase in solidification interval 1/ΔTk. The presence of Al2Cu eutectics as well as the Cu-, Fe-, and Mn-containing phases in the examined samples was demonstrated using scanning electron microscopy.
A paste containing Cu(II) formate rods was prepared, and characteristics of sinter bonding at 250°C under a pressure of 10 MPa were investigated to accomplish a high-speed die attachment for wide-bandgap power chips on Cu finish in air. Synthesis of the plate-type Cu formate particles from CuO was accomplished through a wet reaction for 180 min. Cu, formed in situ in the bondline by pyrolysis of the formate during heating for the attachment, was sufficiently active to lead high-speed sintering within a carbon dioxide-hydrogen atmosphere derived from the pyrolysis, and the oxide layer on the Cu finish was reduced by the hydrogen. As a result, sinter bonding for 10 min formed a robust bonding with a shear strength approaching 27 MPa.
The paper presents the cellular automaton (CA) model for tracking the development of dendritic structure in non-equilibrium solidification conditions of binary alloy. Thermal, diffusion and surface phenomena have been included in the mathematical description of solidification. The methodology for calculating growth velocity of the liquid-solid interface based on solute balance, considering the distribution of the alloy component in the neighborhood of moving interface has been proposed. The influence of solidification front curvature on the equilibrium temperature was determined by applying the Gibbs Thomson approach. Solute and heat transfer equations were solved using the finite difference method assuming periodic boundary conditions and Newton cooling boundary condition at the edges of the system. The solutal field in the calculation domain was obtained separately for solid and liquid phase. Numerical simulations were carried out for the Al-4 wt.% Cu alloy at two cooling rates 15 K/s and 50 K/s. Microstructure images generated on the basis of calculations were compared with actual structures of castings. It was found that the results of the calculations are agreement in qualitative terms with the results of experimental research. The developed model can reproduce many morphological features of the dendritic structure and in particular: generating dendritic front and primary arms, creating, extension and coarsening of secondary branches, interface inhibition, branch fusion, considering the coupled motion and growth interaction of crystals.
Al-4.5Cu alloys are widely used in aerospace industries due to their low weight and high mechanical properties. This group of aluminium alloys is known as 2xx series and exhibits the highest mechanical properties however this alloy is known to suffer from feedability and high tendency for hot tearing. Al-Si alloys (3xx) have improved fluidity and better feedability particularly by several modifications such as Ti, B or Sr. Eutectic temperature is decreased and mechanical properties can be enhanced. Yet, the strength values of this alloy group cannot reach the values of 2xx series. Therefore, in this study, the effect of Ag addition on the fluidity of Al-4.5Cu alloy has been investigated. Standard size spiral mould was used. The casting temperature was selected to be 770oC. Five castings were made and Weibull statistical approach was used to evaluate the results. In addition, coating of the die with BN was also investigated. It was found that Ag addition and BN coating of the die revealed the most reproducible, reliable and high fluidity values.
Ag and Cu powders were mechanically alloyed using high-energy planetary milling to evaluate the sinter-bonding characteristics of a die-attach paste containing particles of these two representative conductive metals mixed at atomic scale. This resulted in the formation of completely alloyed Ag-40Cu particles of 9.5 µm average size after 3 h. The alloyed particles exhibited antioxidation properties during heating to 225°C in air; the combination of high pressure and long bonding time at 225°C enhanced the shear strength of the chip bonded using the particles. Consequently, the chips sinter-bonded at 225°C and 10 MPa for 10 min exhibited a sufficient strength of 15.3 MPa. However, an increase in bonding temperature to 250°C was detrimental to the strength, due to excessive oxidation of the alloyed particles. The mechanically alloyed phase in the particle began to decompose into nanoscale Ag and Cu phases above a bonding temperature of 225°C during heating.
Al-CuO is a thermite material exhibiting the exothermic reaction only when aluminum melts. For wide spread of its application, the reaction temperature needs to be reduced in addition to the enhancement of total reaction energy. In the present study, a thermite nanocomposite with a large contact area between Al and CuO was fabricated in order to lower the exothermic reaction temperature and to improve the reactivity. A cryomilling process was performed to achieve the nanostructure, and the effect of composition on the microstructure and its reactivity was studied in detail. The microstructure was characterized using SEM and XRD, and the thermal property was analyzed using DSC. The results show that as the molar ratio between Al and CuO varies, the fraction of uniform nanocomposite structure was changed affecting the exothermic reaction characteristics.
Cu-Ni composite nanoparticles were successfully synthesized by electrical explosion of wire (EEW) method. Cu-Ni alloy and twisted wires with various Ni contents were used as the feeding material for a 3 kV charging voltage EEW machine in an ethanol ambient chamber. The phase structure and magnetic properties of the as-fabricated samples were studied. It was established that the prepared powders after drying have a spherical form with the particle size is under 100 nm. XRD analysis indicated that the nanopowders consisted of binary Cu-Ni phases. Only pure phases of the intermetallic compound Cu-Ni (Cu0.81Ni0.19 and Cu3.8Ni) were observed in the XRD patterns of the samples. The synthesized intermetallic Cu-Ni alloy nanopowders reveal magnetic behaviors, however, the lower Ni content samples exhibited paramagnetic behaviors, meanwhile, the higher Ni content samples exposed ferromagnetic properties.
Cu-Al-based high temperature shape memory alloys are preferred commonly due to their cheap costs and shape memory properties. In recent years, studies have been conducted on developing and producing a new type of Cu-Al based shape memory alloy. In this study, the CuAl-Cr alloy system, which has never been produced before, is investigated. After production, the SEMEDX measurements were made in order to determine the phases in the Cu84–xAl12Crx+4 (x = 0, 4, 6) (weight %) alloy system; and precipitate phases together with martensite phases were detected in the alloys. The confirmations of these phases were made via x-ray measurements. The same phases were observed by XRD diffractogram of the alloys as well. The values of transformation temperature of alloys were determined with Differential Scanning Calorimetry (DSC) at 20°C/min heating rate. According to the DSC results, the transformation temperature of the alloys varies between 320°C and 350°C. This reveals that the alloys show high temperature shape memory characteristics.
Purpose: The influence of age-hardening solution treatment at temperature 515 degrees centigrade with holding time 4 hours, water quenching at 40 degrees centigrade and artificial aging by different temperature 130, 150, 170 and 210 degrees centigrade with different holding time 2, 4, 8, 16 and 32 hours on changes in morphology of Fe-rich Al15(FeMn)3Si2and Cu-rich (Al2Cu, Al-Al2Cu-Si) intermetallic phases in recycled AlSi9Cu3 cast alloy. Material/Methods: Recycled (secondary) AlSi9Cu3 cast alloy is used especially in automotive industry (dynamic exposed cast, engine parts, cylinder heads, pistons and so on). Microstructure was observed using a combination of different analytical techniques (scanning electron microscopy upon standard and deep etching and energy dispersive X-ray analysis – EDX) which have been used for the identification of the various phases. Quantitative study of changes in morphology of phases was carried out using Image Analyzer software NIS-Elements. The mechanical properties (Brinell hardness and tensile strength) were measured in line with STN EN ISO. Results/Conclusion: Age-hardening led to changes in microstructure include the spheroidization of eutectic silicon, gradual disintegration, shortening and thinning of Fe-rich intermetallic phases and Al-Al2Cu-Si phases were fragmented, dissolved and redistributed within alpha-matrix. These changes led to increase in the hardness and tensile strength in the alloy.
Copper have always been an important material and incorporation of elements into copper for property enhancement. Bronze is a relevant cuprous alloy which is important for many industrial and automotive applications like bearings and machineries. The present research is directed towards the fabrication and tribological analysis of regular bronze (Cu-6Sn) and metal matrix composites reinforced with varying particle sized SiC ceramic reinforcement (30, 35 and 40 μm). The developed specimens were subjected to wear analysis according to ASTM standards, to identify the tribological properties utilizing a pin on disk tribometer. It was noted that the wear rates of developed MMC’s phenomenally decremented with an increase in size of SiC particle reinforcement. Also, the test parameters were influential in altering the wear rates to notable margins. The standard scanning electron microscopy techniques aided in identifying the influence of adhesive wear on the specimen surface.
Monitoring the solidification process is of great importance for understanding the quality of the melt, for controlling it, and for predicting the true properties of the alloy. Solidification is accompanied by the development of heat, the magnitude of which depends on the different phases occurring during solidification. Thermal analysis is now an important part of and tool for quality control, especially when using secondary aluminium alloys in the automotive industry. The effect of remelting on the change of crystallization of individual structural components of experimental AlSi9Cu3 alloy was determined by evaluation of cooling curves and their first derivatives. Structural analysis was evaluated using a scanning electron microscope. The effect of remelting was manifested especially in nucleation of phases rich in iron and copper. An increasing number of remelts had a negative effect after the fourth remelting, when harmful iron phases appeared in the structure in much larger dimensions.