The paper presents the research results on the influence of the parameters of the Dual Rolls Equal Channel Extrusion (DRECE) process on the microstructure and mechanical properties of pure copper. The research was conducted for two vari-ants of the DRECE channel geometry - with extrusion angles of 103° and 98°. Mi-crostructure observations were performed using optical and electron microscopy with backscattered electron diffraction (EBSD). Mechanical properties were deter-mined based on Vickers hardness measurements and tensile tests. The results showed that intense changes in mechanical properties occurred during the first DRECE pass, while subsequent passes led to further moderate strengthening. The values of yield strength (YS) and ultimate tensile strength (UTS) for both DRECE angles were characterized by low anisotropy. The results of the mechanical prop-erty tests indicate that, for pure copper, a lower extrusion angle provides higher ductility at comparable YS and UTS values. EBSD analysis showed noticeable mi-crostructure segmentation and an increase in the proportion of fine grains. IPF maps showed a varied crystallographic orientation after DRECE, with no tendency to form a distinct texture direction.
This study characterized the hot-deformation behavior of G55 steel used in wheel-hub-bearing inner rings and obtained true stress-strain curves from compression tests. A three-stage die-forging route, comprising upsetting, pre-forging, and final forging, was simulated in DEFORM-3D. An L₉(3³) orthogonal design with a smaller-the-better signal-to-noise (S/N) analysis was used to reduce the maximum forming load. The influence of the investigated factors decreased in the order initial billet temperature, shear-friction factor, and upper-die velocity. The lowest simulated load was 1.29 × 10⁷ N at 1200 °C, a friction factor of 0.3, and an upper-die velocity of 100 mm·s⁻¹. Trial forgings produced under these conditions were fully filled and showed no visible surface defects. The optimized process therefore provides a feasible process window for manufacturing the investigated inner ring.
Cu–Al–Mn shape memory alloys (SMAs) are attractive functional materials owing to their thermoelastic martensitic transformation, which enables the shape memory ef-fect, superelasticity, and elastocaloric response. However, their practical application requires precise control of the transformation temperatures. In this study, the effect of Sn addition on the chemical homogeneity, microstructure, hardness, and transfor-mation temperatures of as-cast Cu–Al–Mn–Sn alloys was investigated. CuAl9Mn9.5-based alloys with different Sn contents were fabricated by suc-tion-assisted gravity casting, and their compositions were analyzed by ener-gy-dispersive X-ray spectroscopy. Differential scanning calorimetry revealed that Sn addition systematically decreased the Ms, Mf, As, and Af temperatures. A pronounced shift was already observed after adding 0.78 wt. % Sn, which reduced Af from 102.4 to 23.4 °C. Further Sn additions shifted the transformation interval into the sub-zero temperature range, with Af reaching −61.1 °C at 2.62 wt. % Sn. The transfor-mation-temperature changes were accompanied by a transition from martensitic to austenitic room-temperature microstructure and increased hardness. These results demonstrate that Sn addition is an effective approach for tailoring the transformation temperature range of Cu–Al–Mn SMAs while maintaining casting consistency and chemical uniformity.
Under the “dual carbon” policy, efficient utilization of upgraded vanadium-titanium magnetite has become increasingly important for high-proportion pellet smelting. This study investigates the effects of preheating temperature, preheating time, roasting temperature, and roasting time on the compressive strength and microstructural evolution of fluxed Baima pellets with a basicity of 1.3 using an orthogonal experimental design. Roasting temperature had the greatest influence on compressive strength, followed by roasting time, preheating time, and preheating temperature. Range analysis predicted an optimal factor-level combination of 1000 °C/20 min/1300 °C/15 min, while the highest experimentally measured compressive strength, 2806.2 N/P, was obtained in experiment No. 7 at 1000 °C/10 min/1300 °C/15 min. With increasing roasting temperature, hematite sintering was enhanced, the liquid-phase fraction increased, porosity decreased, and hematite grains grew substantially, resulting in a denser pellet structure.
Aluminum Alloy 6061-T6 is widely used in engineering applications because of its favorable mechanical properties, corrosion resistance, and formability. This study investigated the effect of a single remelting and recasting cycle on the microstructure and spatial distribution of microhardness of Aluminum 6061-T6. The alloy was remelted at approximately 800 °C and gravity cast into a metal mold. Microstructural characterization was performed using optical metallurgical microscopy, while Vickers microhardness was measured at multiple locations across the casting. The wrought material exhibited a relatively homogeneous microstructure with fine and uniformly distributed microstructural features and an average hardness of 134 HV0.5. After remelting and recasting, the average hardness decreased to approximately 89 HV0.5, with values ranging from 80 HV0.5 to 103 HV0.5. Optical microscopy showed a coarser and more heterogeneous microstructure after recasting, together with features consistent with casting-related imperfections. The observed reduction and spatial variation in microhardness were associated with the transition from the original precipitation-hardened T6 condition to a more heterogeneous as-cast microstructure.
