Binary chromium carbides display excellent wear resistance, extreme stiffness and oxidation resistance under high temperature. The influence of applied pressure on electronic structure, elastic behavior, Debye temperature and hardness of Cr₇C₃, Cr₃C₂ and Cr₂₃C₆ have been investigated by the density functional theory (DFT) method. The results reveal that lattice parameters and formation enthalpy display an inverse relationship with applied pressure, and Cr₃C₂ exhibited optimal structural stability. Moreover, Cr-C orbital hybridization tends to be stronger due to the decreased partial density of states (PDOS) of the Cr atom. The difference in electronic distribution of binary carbides has also been investigated, which confirmed that overall orbital hybridization and covalent characteristics has been enhanced. The theoretical hardness was elevated according to the higher bond strength and bond density. In accordance with structural stability data, Cr₃C₂ has shown maximum theoretical hardness. Furthermore, the anisotropic nature of hardness has been evaluated with external pressure. Cr₃C₂, and the highest isotropic hardness behavior along with an increase in hardness values with increasing pressure has been observed. In addition, the variation in Debye temperatures of binary chromium carbides under applied pressure has also been predicted. The results provide a theoretical insight into electronic, mechanical and thermodynamic behavior of three binary chromium carbides and show the potential of these novel carbides in a wide range of applications.

A profound overview of the recent development for on-time, on-demand hydrogen production from light metal-based hydrolysis is presented. Hydrogen energy is one of the clean and renewable energy sources which has been recognized as an alternative to fossil fuels. In addition, aluminum is the most suitable light activity metal for hydrolysis materials attributed to its safety, environmental friendliness, high-energy density, inexpensive, and low density with high strength ratio. In general, dense oxide films formed act as a barrier on aluminum surfaces. Accordingly, effective removal of the oxide film is a key measure in solving the Al–water reaction. In this review, recent advances in addressing the main drawbacks including high-purity aluminum with acid–alkali solutions, nano-powders of aluminum or composite with acid–base solutions, ball-milled nano-powders, alloying blocks, and gas atomization powders are summarized. The characteristics of these three technologies and the current research progress are summarized in depth. Moreover, it is essential to promote low-cost aluminum-based materials based on effective hydrogen production efficiency and explore ways for practical large-scale applications.

In this study, a Cr₃C₂-NiCr cermet cladding layer was prepared on the surface of Q235 steel via a high-speed laser cladding method. The effects of laser power, scanning speed, and overlap rate on the microstructure, cladding quality, and interfacial elements diffusion of Cr₃C₂-NiCr/Q235 steel were studied. The results show that there was an obvious transition layer at the interface of the Cr₃C₂-NiCr cladding layer and Q235 steel, indicating that the Cr₃C₂-NiCr cladding layer had an adequate metallurgical bond with the matrix. Fe, Cr, and Ni were diffused distinctly between the cladding layer and the matrix. The height and width of the Cr₃C₂-NiCr cladding layer increased, while the dilution rate decreased with the increase in the laser power. The maximum thickness of the transition layer was about 50 μm for the 6 mm/s sample, the weld heat affected zone was smaller, and it was shown that the productivity can be effectively improved. The sample with a 40% overlap rate exhibited the best flatness. The optimal laser power, scanning speed, and overlap rate of the Cr₃C₂-NiCr/Q235 steel were 1500 W, 6 mm/s, and 40%, respectively.

As a pre-treatment process in the pre-passivation of stainless steel, pickling treatment has a significant effect on the formation of the pre-passivation film. Thus, the surface composition and defects of Super 13Cr martensitic stainless steel (Super 13Cr) were evaluated under different pickling parameters to further improve the corrosion resistance of the pre-passivation film. The samples were prepared using the acid immersion method and by changing the immersion duration and the acid concentration. The inclusion and chemical composition on the Super 13Cr surface were characterized via a scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). The pickling treatment contributes little to the morphology, dimension, and other characteristic parameters of the inclusions. With the increasing duration and acidification concentration, the Cr content on the surface of Super 13Cr increases initially and then decreases. By contrast, the Fe content decreases initially and then increases. The pickling parameters corresponding to the lowest Fe content and the highest Cr content are identical, i.e., the exposure duration is 50 s and the acid concentration is 48 g/L. The pickling treatment in this case could be divided into two stages: outer film dissolution and inner film dissolution. The pickling parameters basically contribute little to the defects of martensitic stainless steel but can significantly affect the surface Cr and Fe content. Retaining the Cr-enriched inner layer could improve the content of Cr in the pre-passivation film and then improve the corrosion resistance of the film. Thus, compared with the original sample with native film, the corrosion resistance of the sample with a Cr-enriched inner layer improved by a factor of about 40.

In this study, TiB₂/7075 aluminum matrix composites were prepared via in situ synthesis. It was found that TiB₂ particles are mainly quadrate. Large TiB₂ particles (1–2 μm) agglomerate at grain boundaries, but most of the particles are on the submicron scale. Adding 4.5 wt.% TiB₂ particles effectively optimizes α-Al grains in the 7075 aluminum alloy. By combining in situ reinforcing particles with the self-stirring effect of a serpentuator, rheocasting of the 7075 aluminum alloy was achieved in a simple and economical way. The average grain size of the specimen after rheocasting and heat treatment was smaller than 33 μm, and the shape factors were greater than 0.85. The wear resistance of the 4.5 wt.% TiB₂/7075 aluminum matrix composite that was prepared via rheocasting and gravity casting was tested with loads of 30, 60, 90, and 120 N at a friction speed of 0.15 m/s for a duration of 30 min. Because of the optimized microstructure and increased hardness, the wear resistance of the 4.5 wt.% TiB₂/7075 aluminum matrix composite was significantly better than that of the 7075 aluminum alloy, and the wear resistance of the rheocast TiB₂/7075 aluminum matrix composite was better than that of the gravity cast one.

Magnesium aluminum alloy has a broad potential utilization because of its high specific stiffness, specific strength, excellent anti-vibration performance and good impact resistance. The main reason for the weakness of the welding strength of magnesium/aluminum as dissimilar metals during the welding process is the Mg₂₃Al₃₀ intermetallic compound. In the present article, first principle calculation methods are introduced to study the thermodynamic properties, structural stability, electronic structure, elastic properties and performance of Mg₂₃Al₃₀ under pressure. The decreasing range of c is greater than that of a, which indicates that the material has anisotropy. Mg and Al atoms in the Mg₂₃Al₃₀ structure are characterized by metal bonds. It can be concluded that Mg₂₃Al₃₀ not only behaves as a stable crystal structure but also has good elastic stability. After determined the ratio of the G/B criterion, Mg₂₃Al₃₀ belongs to the ductile materials. When treated with pressure in the range of 0–6 GPa, the volume modulus B, Young’s modulus E and shear modulus G of Mg₂₃Al₃₀ materials all increase with the pressure, which show its excellent mechanical stability.