Recent Advances in Additive Manufacturing of High Entropy Alloys and Their Nuclear and Wear-Resistant Applications

Alloying has been very common practice in materials engineering to fabricate metals of desirable properties for specific applications. Traditionally, a small amount of the desired material is added to the principal metal. However, a new alloying technique emerged in 2004 with the concept of adding several principal elements in or near equi-atomic concentrations. These are popularly known as high entropy alloys (HEAs) which can have a wide composition range. A vast area of this composition range is still unexplored. The HEAs research community is still trying to identify and characterize the behaviors of these alloys under different scenarios to develop high-performance materials with desired properties and make the next class of advanced materials. Over the years, understanding of the thermodynamics theories, phase stability and manufacturing methods of HEAs has improved. Moreover, HEAs have also shown retention of strength and relevant properties under extreme tribological conditions and radiation. Recent progresses in these fields are surveyed and discussed in this review with a focus on HEAs for use under extreme environments (i.e., wear and irradiation) and their fabrication using additive manufacturing.

On the possibility of replacement of calcium carbonate by a high-performance, economically viable filler in polyethylene composites

Calcium carbonate (CaCO3) is frequently added to polyethylene (PE) as a filler to reduce costs. An alternative to CaCO3, calcium fluoride (CaF2) was proposed in this research. PE/CaCO3 and PE/CaF2 composites in a wide composition range (0–60 wt.%) were prepared through a parallel twin screw extruder. Results indicated better interaction of CaF2 with PE matrix which improved samples yield stress. Statistical analysis showed the filler type was more influential factor on the yield stress while filler loading was not a statistically significant one. In contrast, crystallinity was strongly depended on the filler loading. The dynamic mechanical and rheological investigations revealed that PE/CaF2 composites had higher stiffness at ambient temperature and possessed lower viscosity below 40 wt.% of filler loading compared to PE/CaCO3 which could reduce the processing cost. Therefore, regarding its low price and good functional properties, CaF2 can be a promising alternative to CaCO3.

Thermodynamic assessment of the Sb–S and In–S binary systems

The Sb–S and In–S binary systems were assessed thermodynamically using the CALculation of PHase Diagrams (CAL-PHAD) approach based on the experiment data in the literature. Both phase diagrams revealed a congruent melting compound and liquid immiscibility. Therefore, associate species, Sb2S3 and In2S3, were introduced into the associate model to describe the liquid phase during optimization. The binary intermediate compounds, Sb2S3, InS(α, β), and In6S7, were treated as stoichiometric phases. Considering the wide composition range, In2S3(α, β, γ), were modeled using the sublattice model. A set of self-consistent thermodynamic parameters representing most of the reliable thermodynamic properties and phase diagram information were derived.

The Structures of ZnCl2-Ethanol Mixtures, a Spectroscopic and Quantum Chemical Calculation Study

We report in this article the structural properties, spectral behavior and heterogeneity of ZnCl2-ethanol (EtOH) mixtures in a wide-composition range (1:3 to 1:14 in molar ratios), using ATR-FTIR spectroscopy and quantum chemical calculations. To improve the resolution of the initial IR spectra, excess spectroscopy and two-dimensional correlation spectroscopy were employed. The transformation process was suggested to be from EtOH trimer and EtOH tetramer to EtOH monomer, EtOH dimer and ZnCl2-3EtOH complex upon mixing. The theoretical findings showed that increasing the content of EtOH was accompanied with the flow of negative charge to ZnCl2. This led to reinforcement of the Zn←O coordination bonds, increase of the ionic character of Zn‒Cl bond and weakening and even dissociation of the Zn‒Cl bond. It was found that in some of the ZnCl2-EtOH complexes optimized at the gas phase or under the solvent effect, there existed hydroxyls with a very special interactive array in the form of Cl‒Zn+←O‒H…Cl−, which incredibly red-shifted to wavenumbers <3000 cm−1. This in-depth study shows the physical insights of the respective electrolyte alcoholic solutions, particularly the solvation process of the salt, help to rationalize the reported experimental results, and may shed light on understanding the properties of the deep eutectic solvents formed from ZnCl2 and an alcohol.

Concentration and Size Effects in Electrophysical Properties of Thin Films Based on Permalloy and Silver

Complex study of electrophysical properties (the electrical resistivity r and the temperature coefficient of resistance (TCR) b) of thin-film samples based on ferromagnetic alloy Ni80Fe20 (permalloy) and noble metal Ag in a wide composition range and within the range of thickness 20-100 nm done. Thin films were obtained by the method of electron-beam co-evaporation technique at room temperature. Their composition was investigated using the method of X-ray spectrometry. The phase state was analyzed by the electron diffraction method. It was demonstrated that the crystal structure of thin films stays unchanged during the annealing process to 500 K. The size and concentration dependences of r and b values were obtained. The corresponding maximum and minimum at the concentration of Ag atoms of 50-60 at.% observed at the dependences r(cAg) and b(cAg). Size dependences r(d) and b(d) associated with the size effects in thin-film materials.

Ionic transport and atomic structure of AgI-HgS-GeS2 glasses

Quasi-ternary (AgI)x(HgS)0.5−x/2(GeS2)0.5−x/2 glasses, 10−4≤x≤0.6 were studied over a wide composition range covering nearly 4 orders of magnitude in the mobile cation content. The glasses show a remarkable increase of the ionic conductivity by 12 orders of magnitude and exhibit two drastically different ion transport regimes: (i) a power-law critical percolation at x≲0.04, and (ii) a modifier-controlled conductivity, exponentially dependent on x≳0.1. Using Raman spectroscopy and high-energy X-ray diffraction supported by DFT modelling of the Raman spectra we show that the glass network is essentially formed by corner-sharing CS-GeS4/2 tetrahedra. Mercury sulfide in glasses is dimorphic. The majority of Hg species (70% at x<0.2) exist as two-fold coordinated (HgS2/2)n chains. Silver species have mixed (2I+2S) tetrahedral environment forming either edge–sharing ES-Ag2I2S4/2 dimers or corner-sharing (CS-AgI2/2S2/2)n chains. The relationship between the ionic transport and atomic structure of the glasses is discussed.