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In this study, AlCoCrFeNi–Cu (Cu-based) and AlCoCrFeNi–Ti (Ti-based) high entropy alloys (HEAs) were fabricated using a direct blown powder technique via laser additive manufacturing on an A301 steel baseplate for aerospace applications. The purpose of this research is to investigate the electrical resistivity and oxidation behavior of the as-built copper (Cu)- and titanium (Ti)-based alloys and to understand the alloying effect, the HEAs core effects and the influence of laser parameters on the physical properties of the alloys.

The as-received AlCoCrFeNiCu and AlCoCrFeNiTi powders were used to fabricate HEA clads on an A301 steel baseplate preheated at 400°C using a 3 kW Rofin Sinar dY044 continuous-wave laser-deposition system fitted with a KUKA robotic arm. The deposits were sectioned using an electric cutting machine and prepared by standard metallographic methods to investigate the electrical and oxidation properties of the alloys.

The results showed that the laser power had the most influence on the physical properties of the alloys. The Ti-based alloy had better resistivity than the Cu-based alloy, whereas the Cu-based alloy had better oxidation residence than the Ti-based alloy which attributed to the compositional alloying effect (Cu, aluminum and nickel) and the orderliness of the lattice, which is significantly associated with the electron transportation; consequently, the more distorted the lattice, the easier the transportation of electrons and the better the properties of the HEAs.

It is evident from the studies that the composition of HEAs and the laser processing parameters are two significant factors that influence the physical properties of laser deposited HEAs for aerospace applications.

The purpose of this paper is to explore the possibility of producing Cu-based shape memory alloys (SMA) by means of direct metal laser fabrication (DMLF).

The fabrication approach consists of the combination of laser melting of a metallic powder with heating treatment in a controlled inert atmosphere. Three prospective Cu-Al-Ni alloy compositions were tested, and the effects of laser power, as well as laser exposure time, were verified.

All the processed materials were found to attain microstructures and phase change transformation temperatures typical of this type of SMA.

Further development of this technique will allow for fabrication of large elements with considerable shape memory effect, which are currently not viable due to high cost of nitinol.

This work showed a proof of concept toward the development of DMLF-based additive manufacturing of near net shape components of Cu-based SMAs from elemental powders.

The purpose of this paper is to increase the reliability of manufactured electronics and to reveal reliability significant factors. The experiments were focused especially on the influence of the reflow oven parameters presented by a heating factor.

The shear strength of the surface mount device (SMD) resistors and their joint resistance were analyzed. The resistors were assembled with two Sn/Ag/Cu-based and one Bi-based solder pastes, and the analysis was done for several values of the heating factor and before and after isothermal aging. The measurement of thickness of intermetallic compounds was conducted on the micro-sections of the solder joints.

The shear strength of solder joints based on the Sn/Ag/Cu-based solder alloy started to decline after the heating factor reached the value of 500 s · K, whereas the shear strength of the solder alloy based on the Bi alloy (in the measured range) always increased with an increase in the heating factor. Also, the Bi-based solder joints showed shear strength increase after isothermal aging in contrast to Sn/Ag/Cu-based solder joints, which showed shear strength decrease.

The interpretation of the results of such a comprehensive measurement leads to a better understanding of the mutual relation between reliability and other technological parameters such as solder alloy type, surface finish and parameters of the soldering process.

The inhibition effect and mechanism of benzotriazole 2‐mercaptobenzothiazole with and without the addition of thiourea on dezincification of Cu‐based alloys have been studied. The measurement were carried out in the solution of 3.5% NaCl with 0.025% Na2SO44 at pH adjusted to 3.53 and at 29° and 60°C. Electrical measurements were conducted galvanostatically (2.14 mA/cm2) and potentiostatically (−200 mV vs. SCE) for 3 hr in the test solution. The performance of the inhibitor were assessed in terms of (1) dissolution of Cu/Zn during polarization and (2) electric charge measurement. The inhibition efficiency calculated from electric charge was in good conformity with the results of chemical analysis of Cu/Zn dissolution during polarization in the test solution. The results were discussed in the light of adsorption theory.

The purpose of this paper is to examine the microstructure and evaluate the intermetallic compounds in the following lead‐free solder alloys: Sn_98.5Ag_1.0Cu_0.5 (SAC105) Sn_97.5Ag_2.0Cu_0.5 (SAC205) Sn_96.5Ag_3.0Cu_0.5 (SAC305) and Sn_95.5Ag_4.0Cu_0.5 (SAC405).

X‐ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to identify the main intermetallics formed during solidification. Differential scanning calorimetry (DSC) was used to investigate the undercooling properties of each of the alloys.

By using XRD analysis in addition to energy dispersive spectroscopy (EDS) it was found that the main intermetallics were Cu₆Sn₅ and Ag₃Sn in a Sn matrix. Plate‐like ε‐Ag₃Sn intermetallics were observed for all four alloys. Solder alloys SAC105, SAC205 and SAC305 showed a similar microstructure, while SAC405 displayed a fine microstructure with intermetallic phases dense within the Sn matrix.

Currently, low‐silver content SAC alloys are being investigated due to their lower cost, however, the overall reliability of an alloy can be greatly affected by the microstructure and this should be taken into consideration when choosing an alloy. The size and number of Ag₃Sn plate‐like intermetallics can affect the reliability as they act as a site for crack propagation.

The purpose of this study was to investigate the polyacrylic polymer/Al₂O₃ as a new nanocomposite coating to protect brass and Al-bronze in 3.5% NaCl and the role of alumina formulation on their protection efficiency

The corrosion efficiency of the nanocomposite coating (NCC) was evaluated by open circuit potential and electrochemical impedance spectroscopy (EIS).

The protection efficiency was more in the case of Al-bronze even for the same formulation of alumina NCC indicated the Cu substrate contribution. The Cu oxides in alloys and Al₂O₃ from the NCC and Al-bronze were responsible for this protection.

All the techniques supported each other, the presence of alumina was responsible for the corrosion protection efficiency.

The purpose of this study was to examine the influence of adding a small amount of Ti to a Cu-based alloy, specifically the commercial Hyper Titanium Copper alloy (C1990 HP), which contains Cu-3.28 wt.% Ti, on its interfacial reaction with Sn-9.0 wt.% Zn (SnZn) solder, using the liquid/solid reaction couple technique.

The SnZn/C1990 HP couples were subjected to a reaction temperature of 240–270°C for a duration of 0.5–5 h. The resulting reaction couple was characterized using a scanning electron microscope, energy dispersive spectrometer, electron probe microanalyzer and X-ray diffractometer.

It was observed that the scallop-shaped CuZn5 and planar Cu5Zn8 phases were formed in almost all SnZn/C1990 HP couples. With increased reaction duration and temperature, the Cu-rich intermetallic compound (IMC)-Cu5Zn8 phase became a dominant IMC formed at the interface. The total thickness of the IMCs was increased with the increase in the reaction duration and temperature. The IMC growth obeyed the parabolic law, and the IMC growth mechanism was diffusion controlled. The activation energy of the SnZn/C1990 HP couple was 64.71 kJ/mol.

This article presents an analysis of the IMC thickness in each sample using ImageJ software, followed by kinetic analysis using Origin software at various reaction temperatures of SnZn/C1990 HP in liquid/solid couples. The study also includes detailed reports on the morphology, interface composition and X-ray diffraction analysis, as well as the activation energy. The findings can serve as a valuable reference for electronic packaging companies that utilize C1990 HP substrates.

The purpose of this paper is to analyze and investigate heat accumulation caused by temperature changes and interface microstructure effected by element diffusion.

Al/Cu bimetallic structure is initially manufactured through laser powder bed fusion process. To minimize trial and error, finite element modeling is adopted to simulate temperature changes on the Al-based and Cu-based substrate.

The results show that forming pure copper on Al-based substrate can guarantee heat accumulation, providing enough energy for subsequent building. The instantaneous laser energy promotes increase of diffusion activation energy, resulting in the formation of transition zone derived from interdiffusion between Al and Cu atoms. The interface with a thickness of about 22 µm dominated by Kirkendall effect moves towards Al-rich side. The interface microstructure is mainly composed of a-Al, a-Cu and CuAl2 phase.

The bonding mechanism of Al/Cu interface is atom diffusion-induced chemical reaction. The theoretical basis provides guidance for structural design and production application.

The purpose of this paper is to evaluate, by experimental investigation, the wear and friction performances of porous bearings under different operating conditions.

Two different compositions of self‐lubricating bearings were chosen: 90 percent Cu+10 percent Sn and 90 percent Cu+9 percent Sn+1 percent C. The bearings were produced with their final densities of 80 and 85 percent, and pressed at room temperature and high temperature.

The wear and friction properties of the sample bearings were determined at different running conditions such as temperature, applied load, and sliding speed. The variations of the weight loss with the sliding distance for different test conditions were presented. The results show that the weight loss and friction coefficient increase with the increasing sliding speed, density and temperature.

The wear and friction properties of the sample bearings were determined at different running conditions such as temperature, applied load, and sliding speed.

This study aims to present a more accurate lifetime prediction model considering solder chemical composition.

Thermal cycling and standard creep tests as well as finite element simulation were used.

The study found lower error in the solder joint lifetime evaluation. The higher the Ag content is, the higher the lifetime is achieved.

It is confirmed.