China Iron and Steel Research Institute Group

Al/Mg bimetallic composites have drawn considerable attention for their promising lightweight applications in sectors such as the aerospace and automotive industries. In these systems, the interfacial behavior critically governs the overall performance and reliability. In this research, the molecular dynamics (MD) simulation was employed to systematically study the effects of pouring temperatures (923 K, 973 K, and 1023 K) and preheating temperatures (373 K, 473 K, and 573 K) on the interfacial diffusion behavior and fracture mechanism of the polycrystalline Al/Mg bimetallic system. The results indicate that the influencing rule of pouring temperatures and preheating temperatures on the interfacial diffusion behavior is consistent. Specifically, the diffusion coefficient of Mg atoms is higher than that of Al atoms, while the diffusion distance of Al atoms is significantly greater than that of Mg atoms. As the temperature increases, the thickness of the interfacial transition layer correspondingly rises. However, the effects of these two parameters on tensile fracture behavior demonstrate notable discrepancies. Specifically, the fracture mode evolves with pouring temperature, transitioning from being mediated solely by dislocations to being co-mediated by twins and dislocations. In contrast, the fracture mechanism remains solely dislocation-controlled, regardless of the preheating temperature. In addition, all the models fractured at the interface between the diffusion layer and the Mg matrix. The optimal tensile strength of 1.850 GPa was achieved at a pouring temperature of 923 K and a preheating temperature of 473 K, representing an improvement of approximately 52% compared to the lowest value recorded in the study. This research offers significant theoretical insights for the rational optimization of preparation parameters and an in-depth understanding of fracture mechanisms in Al/Mg bimetallic systems.

Abstract The tensile strength of railway wheels is a crucial mechanical property in the quality assessment and safe service of wheels. Conventional tensile testing imposes strict requirements on specimen size and can only test one specimen in each experiment, hindering its application to the characterization of the tensile strength distribution of train wheels with complex structures. In this study, six-channel mechanical testing of miniature specimens was applied to characterize the tensile properties of high-speed rail wheel rims, enabling analysis of the correlations between micro-zone tensile properties and microstructures of high-speed rail wheels. The results showed that micro-zone tensile strength gradually decreased as the depth of the micro-zone increased from the tread surface to the radial interior. Moreover, both micro-zone tensile strength and plastic extension strength also gradually decreased as the pearlite lamellar spacing and ferrite area fraction increased. Micro-zone tensile strength and plastic extension strength showed good correlations with pearlite lamellar spacing and ferrite area fraction, with polynomial best-fit curves presenting correlation coefficients >0.95. The results of this study could serve as a technical reference for studying the tensile properties of high-speed rail wheel steel.

Abstract Gadolinium (Gd) is the benchmark magnetocaloric material, yet its performance requires optimization in working temperature range, refrigeration capacity (RC) and heat exchange capacity. Here, we address this by a synergistic strategy combining Co alloying (to create an in-situ dual-phase magnetocaloric system) and the melt-extraction technique (to directly shape the alloy into microwires). This approach fabricates Gd 87.5 Co 12.5 (at.%) crystalline/crystalline composite microwires. The resulting microstructure comprises a Gd-rich matrix embedded with magnetocaloric Gd 3 Co phase, both of which are crystalline. This dual-phase architecture yields a remarkable magnetic entropy change (-Δ S m ) profile, which delivers an ultra-broad effective temperature span ( δT ) of 218.5 K (defined between the outer half-maximum points of the dual-peak magnetic entropy change vs temperature curve, 107.6–326.1 K) and a high RC of 658.7 J/kg under 5 T. To our knowledge, this work represents the first investigation of the magnetocaloric effect (MCE) in Gd-based crystalline/crystalline composite microwires. More importantly, it validates a dual-route design paradigm: phase-composition engineering for broadened δT and RC, coupled with morphology engineering via melt-extraction for enhanced heat exchange. This work establishes a new paradigm for designing next-generation magnetocaloric materials with integrated performance enhancements, particularly for efficient magnetic refrigeration in applications like gas liquefaction.

The quantity, size, and distribution of non-metallic inclusions in High-Strength Low-Alloy (HSLA) steel critically influence its service performance. Conventional detection methods often fail to adequately characterize extreme inclusion distributions in large-section components. This study developed an integrated full-process inclusion analysis system combining high-precision motion control, parallel optical imaging, and laser spectral analysis technologies to achieve rapid and automated identification and compositional analysis of inclusions in meter-scale samples. Through systematic investigation across the industrial process chain—from a dia. 740 mm consumable electrode to a dia. 810 mm electroslag remelting (ESR) ingot and finally to a dia. 400 mm forged billet—key process-specific insights were obtained. The results revealed the effective removal of Type D (globular oxides) inclusions during ESR, with their counts reducing from over 8000 in the electrode to approximately 4000–7000 in the ingot. Concurrently, the mechanism underlying the pronounced enrichment of Type C (silicates) in the ingot tail was elucidated, showing a nearly fourfold increase to 1767 compared to the ingot head, attributed to terminal solidification segregation and flotation dynamics. Subsequent forging further demonstrated exceptional refinement and dispersion of all inclusion types. The billet tail achieved exceptionally high purity, with counts of all inclusion types dropping to extremely low levels (e.g., Types A, B, and C were nearly eliminated), representing a reduction of approximately one order of magnitude. Based on these findings, enhanced process strategies were proposed, including shallow molten pool control, slag system optimization, and multi-dimensional quality monitoring. An intelligent analysis framework integrating a YOLOv11 detection model with spectral feedback was also established. This work provides crucial process knowledge and technological support for achieving the quality control objective of “known and controllable defects” in HSLA steel.