To investigate the forming mechanism of shaped tubes in roll forming of circular tubes, this study conducted roll forming experiments on shaped tubes with different materials and geometries. Using a 30 × 30 mm Q345B square tube as the target, samples were taken from both the planar and corner regions for mechanical property testing and microstructural characterization. The results show that in the uniaxial tensile tests of the planar region, 20Mn2 exhibited the highest tensile strength. Fracture surfaces of all materials displayed evident dimples, second-phase particles, and tear ridges, indicating significant ductile fracture characteristics. In the hardness tests of the corner region, the inner side showed noticeably higher hardness than the outer side, with the maximum value occurring in the inner area. The dislocation density in the inner corner was greater than in the middle and outer regions, a result of metal flow in the corner area. TEM observations of the corner region revealed substantial dislocation pile-ups at grain boundaries, demonstrating severe plastic deformation in this zone.
The fundamental mechanisms of hydrogen atom incorporation into the tetragonal lattice of the Pd3Mn intermetallic compound (space group I4/mmm, file no. 139) are studied using density functional theory (DFT) and X-ray diffraction. The crystal structure is found to form octahedral interstices coordinated exclusively by palladium atoms (Pd6), which is due to the coincidence of their electronegativities ( χ_Pd = χ_H = 2.20 ) and the optimum cavity radius ( 0.53 Å). Dissolution energy calculations show that the dissolution is exothermic for a concentration n ≈ 1.0 (Pd3Mn–nH), after which the dissolution energy decreases due to repulsion between H atoms. An analysis of the projected density of electronic states (PDOS) has revealed the following key effects: a shift of the Fermi level by 0.4 eV deep into the valence band, the appearance of a hybrid peak at ε ≈ −2.5 eV (s(H)–d(Pd)), and the suppression of DOS at the Fermi level indicating an increase in thermodynamic stability. The incorporation of even a single H atom leads to a local lattice distortion and a symmetry lowering from tetragonal (I4/mmm) to triclinic (P1), which is a direct consequence of electronic density localization and the formation of a directional covalent-like bond. The maximum theoretical hydrogen capacity is estimated at 0.80 wt
This article investigates the process of electrochemical removal of phosphate ions from washing solutions generated in aluminum production. A distinctive feature of these solutions is the presence of a significant concentration of aluminum (46.42 g/L) in the form of [Al(OH)4]–, in addition to phosphate ions (up to 1.7 g/L). The influence of operational parameters—initial pH, process time (τ), initial phosphate ion concentration, interelectrode distance, and current density—on the efficiency of phosphate removal by electrocoagulation using aluminum electrodes was studied. It is shown that electrochemical dissolution of the aluminum anode followed by hydrolysis of Al3+ ions in solution leads to the formation of an amorphous coagulant precipitate, aluminum hydroxide. It was established that electrolysis of the solution with an aluminum anode at a current density of J = 10 mA/cm2 results in phosphate ion removal exceeding 90 SO_4^2 - , PO_4^3 - , F–, Cl–, VO_4^3 - ) present in washing solutions obtained during alunite processing on the degree of phosphate removal was also evaluated.
The deep drawing of multi-layer sheets is crucial for the production of lightweight, high-strength components in the automotive and aerospace industries. This study examines the drawing depth of St12/Al 3105 two-layer sheets in square deep drawing through both experimental and numerical approaches. The Gurson–Tvergaard–Needleman (GTN) damage model, implemented via a UMAT subroutine in ABAQUS/CAE, predicts material failure with errors below 1
This study investigates the hardening characteristics of magnetite-anthracite-calcium hydroxide composite pellets carbonated at 600°C in a CO2 atmosphere, with the objective of ensuring adequate mechanical strength for pre-reduction in shaft kilns. During carbonation, Ca(OH)2 and Fe3O4 were transformed into CaCO3 and Fe2O3, respectively. The influence of iron ore particle size on the post-carbonation strength of composite pellets was systematically examined. Results demonstrate that reducing particle size accelerates the carbonation reaction and significantly enhances pellet strength. Specifically, carbonated pellets prepared from conventional magnetite ore exhibited a compressive strength of approximately 262 N/pellet, whereas those fabricated from ultrafine-pulverized ore achieved strengths reaching 800 N/pellet. These findings indicate that ultrafine-pulverized magnetite concentrate, in combination with coal and calcium hydroxide, can be utilized to produce composite pellets suitable for pre-reduction in shaft kilns utilizing waste heat from smelting reduction furnaces.
