Alloys

This study experimentally investigates the effect of oxide film thickness on the amplitude of laser-induced stress waves in AISI W1-7 carbon steel. Oxide layers of approximately 0.045 μm (straw-yellow) and 0.07 μm (blue) were synthesized via controlled heating using a free-running YAG:Nd3+ laser. The work used a Q-switched ruby laser (λ = 0.69 μm; FWHM = 25–30 ns; E up to 1.5 J) to generate intense stress waves. The displacement of the sample’s free surface was recorded using a Michelson interferometer with a probing He–Ne laser (λ = 0.6328 μm), which was used to construct the “pressure–time” relationship. It has been established that oxide films with thicknesses of 0.045 and 0.07 μm increase the wave amplitude by 1.15 and 1.4 times, respectively, relative to pure steel, which is associated with enhanced optical absorption and thin-film interference at the laser pump wavelength. Furthermore, the quasi-linear dependence of the stress wave amplitude on the laser pulse energy (0.7–1.5 J) indicates the absence of plasma shielding within this energy range. These findings suggest that controlled thermal oxidation can serve as an effective, clean absorptive coating to optimize laser shock peening (LSP) processes.

In this paper, we experimentally investigated the integrated processing of high-iron Kazakh bauxites by reducing smelting of ore–coke–lime briquettes to produce an Fe-Al-Si metallic alloy, which is of potential interest for steel deoxidation, together with calcium-aluminate slag, which is of potential interest for alumina extraction. Briquettes containing bauxite, metallurgical coke (10–20 wt.%), and freshly calcined lime (10 wt.%, constant) were melted in a muffle furnace at a temperature of 1200–1450 °C. Complete separation of metal and slag was achieved at 1400–1450 °C, whereas at 1200–1350 °C, separation remained incomplete. Changing the coke/bauxite mass ratio in the charge from 0.125 to 0.286 increased the total content of metallic Si, Al and Fe in the recovered metallic product from 77.1 to 98.66 wt.%, according to X-ray fluorescence (XRF) analysis after two-stage magnetic separation; the metallic product obtained with a coke/bauxite ratio of 0.286 in the charge contained 72.8% Fe, 23% Al and 2.86% Si (with minor impurities of Ti, Mn and Cr), while the associated slag was represented mainly by CaO (59.5%) and Al2O3 (34.0%). These slag characteristics indicate its potential suitability for alumina extraction or as a filler for structural concrete. The proposed route represents a potentially low-waste alternative for processing high-iron bauxites that are poorly suited to the classical Bayer process, avoiding the direct formation of red mud and supporting Kazakhstan’s transition toward closed-loop bauxite processing.

Nanostructured tungsten–copper (W–Cu) composites are promising materials for high-heat-flux components and advanced thermal management; however, their processing is limited by a high positive enthalpy of mixing of ~35.5 kJ/mol and weak interfacial bonding. This study provides a thermodynamic and kinetic justification for a technological route intended for 70W–30Cu and 75W–25Cu (wt.%) composites using high-energy mechanical activation and spark plasma sintering (SPS). CALPHAD-type calculations identified a critical copper activity plateau a_Cu ≈ 0.33 at 950 °C in the W-rich range, which favors the retention of submicron grains of 200–300 nm by limiting the chemical potential driving force for coarsening. Kinetic modeling via DICTRA predicted the formation of metastable interfacial diffusion zones with a characteristic width of 20–90 nm during short SPS holding times of 150–300 s, enabling the transition from mechanical interlocking to metallurgical bonding. Based on these calculations, a processing window of 950–1050 °C is proposed to achieve a target relative density of ≥97% and electrical conductivity of 35–45% IACS. The results provide a predictive framework for the experimental synthesis of nanostructured pseudoalloys with optimized conductive networks and reinforced tungsten skeletons.