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1. Strength can be controlled by edge dislocations in refractory high-entropy alloys

   https://doi.org/10.1038/s41467-021-25807-w  

   Lee, Chanho; Maresca, Francesco; Feng, Rui; Chou, Yi; Ungar, T.; Widom, Michael; An, Ke; Poplawsky, Jonathan D.; Chou, Yi-Chia; Liaw, Peter K.; et al (December 2021, Nature Communications)

   Abstract Energy efficiency is motivating the search for new high-temperature (high-T) metals. Some new body-centered-cubic (BCC) random multicomponent “high-entropy alloys (HEAs)” based on refractory elements (Cr-Mo-Nb-Ta-V-W-Hf-Ti-Zr) possess exceptional strengths at high temperatures but the physical origins of this outstanding behavior are not known. Here we show, using integrated in-situ neutron-diffraction (ND), high-resolution transmission electron microscopy (HRTEM), and recent theory, that the high strength and strength retention of a NbTaTiV alloy and a high-strength/low-density CrMoNbV alloy are attributable to edge dislocations. This finding is surprising because plastic flows in BCC elemental metals and dilute alloys are generally controlled by screw dislocations. We use the insight and theory to perform a computationally-guided search over 10 7 BCC HEAs and identify over 10 6 possible ultra-strong high-T alloy compositions for future exploration. 

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2. Stabilization of III-nitrides at high temperatures using nitrogen plasma

   https://doi.org/10.1063/5.0257926  

   Moher, Dillon; Shanahan, Reilly; Thimsen, Elijah (April 2025, Applied Physics Letters)

   III-Nitride materials such as gallium nitride (GaN) and indium nitride (InN) are critical for applications in electronics and optoelectronics due to their exceptional properties. However, their high-temperature stability is often limited by decomposition into constituent elements at low nitrogen pressures near or below ambient. This work investigates the use of nonequilibrium nitrogen plasma to stabilize GaN and InN at elevated temperatures and low pressures. Bulk nitride synthesis was demonstrated via plasma-assisted nitridation of Ga and In metals. Following synthesis, the suppression of nitride decomposition at temperatures exceeding the predicted equilibrium limits was accomplished by means of a nonequilibrium nitrogen plasma. Experimental results revealed that the nonequilibrium plasma imparted an additional chemical potential onto the ground state nitrogen by electron impact excitation, stabilizing GaN at 1000 °C and InN at 600 °C for nitrogen partial pressures as low as 10 Pa. With this experimental approach, the chemical potential of excited nitrogen species in the plasma was estimated to be 1.8 eV higher than the ground state value. These findings highlight the potential for plasma-based processing to enable scalable synthesis and stabilization of III-nitrides at high temperatures for advanced material applications. 

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3. Oxides and the high entropy regime: A new mix for engineering physical properties

   https://doi.org/10.1557/adv.2020.295  

   Meisenheimer, P. B.; Heron, J. T. (January 2020, MRS Advances)

   null (Ed.)

   Abstract Historically, the enthalpy is the criterion for oxide materials discovery and design. In this regime, highly controlled thin film epitaxy can be leveraged to manifest bulk and interfacial phases that are non-existent in bulk equilibrium phase diagrams. With the recent discovery of entropy-stabilized oxides, entropy and disorder engineering has been realized as an orthogonal approach. This has led to the nucleation and rapid growth of research on high-entropy oxides – multicomponent oxides where the configurational entropy is large but its contribution to its stabilization need not be significant or is currently unknown. From current research, it is clear that entropy enhances the chemical solubility of species and can realize new stereochemical configurations which has led to the rapid discovery of new phases and compositions. The research has expanded beyond studies to understand the role of entropy in stabilization and realization of new crystal structures to now include physical properties and the roles of local and global disorder. Here, key observations made regarding the dielectric and magnetic properties are reviewed. These materials have recently been observed to display concerted symmetry breaking, metal-insulator transitions, and magnetism, paving the way for engineering of these and potentially other functional phenomena. Excitingly, the disorder in these oxides allows for new interplay between spin, orbital, charge, and lattice degrees of freedom to design the physical behavior. We also provide a perspective on the state of the field and prospects for entropic oxide materials in applications considering their unique characteristics. 

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4. Recent Developments in the Processing of Advanced Materials Using Severe Plastic Deformation

   https://doi.org/10.4028/www.scientific.net/MSF.1016.3  

   Kawasaki, Megumi; Figueiredo, Roberto B.; Langdon, Terence G. (January 2021, Materials Science Forum)

   null (Ed.)

   The processing of bulk metals through the application of severe plastic deformation (SPD), using procedures such as equal-channel angular pressing (ECAP) and high-pressure torsion (HPT), is now well established for the fabrication of materials with exceptionally small grain sizes, usually in the submicrometer range and often having grain sizes at the nanometer level. These grain sizes cannot be achieved using thermo-mechanical processing or any conventional processing techniques. Recently, these procedures have been further developed to process alternative advanced materials. For example, by stacking separate disks within the HPT facility for the synthesis of bulk nanocrystalline metastable alloys where it is possible to achieve exceptionally high hardness, or by pressing powders or metallic particles in order to obtain new and novel nanocomposites exhibiting unusual properties. 

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5. Fabrication of High Strength Al Nanocomposites with Populous TiB2 Nanoparticles

   A Javadi, S Pan (January 2018, Procedia manufacturing)

   High performance lightweight metals offer tremendous potential to improve energy efficiency and system performance for numerous applications. Traditional manufacturing processes such as thermomechanical processing and deformation have reached their limits in further improving the properties of metals. Thus, a new approach is necessary to develop high performance lightweight metals which can offer promising properties. Metal matrix nanocomposite (MMNC) is an excellent approach to produce lightweight metals with improved properties that cannot be achieved by traditional manufacturing. Effective incorporation of a suitable nanoparticles system in a metallic matrix such as aluminum (Al) can improve the performance of the matrix. However, due to the high chemical reactivity and poor wettability of Al with nanoparticles, achieving high volume fraction of nanoparticles incorporation is of a great challenge. Here we show a novel approach to incorporate high volume fraction of titanium diboride (TiB2) nanoparticles in Al matrix. Al-TiB2 nanocomposite microparticles were initially produced via flux assisted solidification processes. Al-TiB2 nanocomposites were produced by cold compaction followed by melting. Scanning electron microscopic (SEM) images revealed that the TiB2 nanoparticles are unfirmly dispersed and distributed in Al matrix. Al-TiB2 nanocomposites with as high as 485.9±16.9 Vickers hardness were successfully produced. Furthermore, the effect of melting time was studied on the hardness of the Al-TiB2 nanocomposites. 

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