To achieve the automation of blast furnace operation, an automatic control system for hot metal temperature (HMT) was developed. Nonlinear model predictive control (NMPC) which predicts up to ten-hour-ahead HMT and calculates appropriate control actions of pulverized coal rate (PCR) was constructed. Simulation validation showed that the NMPC algorithm generates control actions similar to those by the operators and that HMT can be maintained within ±10 °C of the set point. The automatic control system using NMPC was then implemented in an actual plant. As a result, the developed control system suppressed the effects of disturbances, such as the changes in the coke ratio and blast volume, and successfully reduced the average control error of HMT by 4.6 °C compared to the conventional manual operation. The developed control system has contributed to the reduction of reducing agent rate (RAR) and CO₂ emissions. Full article

In situ atomic-scale bending tests of twin-structured Ni nanowires were realised using a homemade deformation device. The results showed that the plastic deformation mechanism in twin-structured Ni nanowires depended on the deformation stage. At the early stages of bending deformation, the plasticity of twin-structured Ni nanowires was controlled by dislocations interacting with the twin boundaries or parallel to them. With increasing bending strain, both dislocation and face-centred cubic–body-centred tetragonal phase transition occurred. At very high bending strain, grain boundaries resulting from the lattice distortion/collapse were formed. This study details the deformation mechanisms of the twin-structured Ni nanowires under bending deformation, which advances the basic understanding of the plasticity mechanisms in metals. Full article

The present work aims to systematically investigate the influence of P content on the microstructure and texture evolution of oxygen-free copper during intermediate annealing and final cold rolling. The microstructure and texture evolution were studied by electron backscattered diffraction and transmission electron microscopy. With the addition of P, the grains refined and a large fraction of low angle grain boundaries (LAGBs) emerged after intermediate annealing. The texture transformed from pure metal type for pure Cu to the α-fiber texture which included brass and Goss texture as P was added. The recrystallization temperature increased with the addition of P, and refined grains after the final cold rolling process. The addition of elemental P would reduce the stacking fault energy, and then influence the transformation of the deformation and recrystallization texture of the copper. Accompanied by the evolution of the deformation texture, the recrystallization cubic texture {001}<100> was suppressed and a strong {236}<385> brass recrystallization texture emerged with the addition of elemental P after the intermediate annealing and subsequent final cold rolling process. Full article

The formed parts of tubes easily interfere with the equipment when forming complex tubes in 3D free bending forming technology. Consequently, to solve the interferential phenomenon, an active deflection method (ADM) to avoid interference was proposed to drive the deformed tube around its axis by controlling the bending die. The method extended the activity freedom of the equipment without installing the additional motion shafting. However, severe section distortion, surface scratches and other forming defects frequently occurred during the implementation of ADM, which reduced the structural strength and pressure resistance of the tubes. A mechanical model was developed to analyze the force state of the tube, and the results showed that the driving force of active deflection was mainly determined by the trajectory radius. The curve of the adopted bell-shaped transition structure was closer to the bending curvature of the tube than the rounded structure, which transformed the guider and the tube from linear contact to surface contact. The simulation and experiment results indicated that adding the trajectory radius could strengthen the rotation torque. The stress concentration in the tube was alleviated after applying the bell-shaped transition structure. Full article

A disordered ε-FeSi crystalline structure was produced by selective laser melting in Fe_92.4Si_3.1B_4.5 powder alloys fabricated with different laser powers at a laser scanning speed of 0.4 m/s. The phase formation, microstructure, roughness, microhardness, and hyperfine and magnetic properties were studied using X-ray diffraction, scanning electron microscopy, atomic force microscopy, a profilometer, a microdurometer, transmission ⁵⁷Fe Mössbauer spectrometry and vibrating sample magnetometry. The aim of this work was therefore to study the effect of laser power on the phase formation, microstructure, morphology, and mechanical, hyperfine and magnetic properties. The XRD patterns revealed the coexistence of a bcc α-Fe_0.95Si_0.05, a tetragonal Fe₂B boride phase and a disordered ε-FeSi type structure. The existence of the disorder was confirmed by the presence of different FeSi environments observed in the Mössbauer spectra. The Fe₂B boride contained about 51–54% of Fe atoms. The porosity and roughness decreased whereas laser power increased. The sample produced with a laser power of 90 W had a smooth and dense surface, high microhardness (~1843 Hv) and soft magnetic properties (saturation magnetization Ms = 200 emu/g and coercivity Hc = 79 Oe). Full article

Two steels with a base composition of Fe-0.2C-0.8Mn-1.2Cr (wt%) but with different niobium (Nb) contents (0.02 and 0.03 wt%) were employed to study the effect of precipitate evolution on the softening resistance in the austenite region under elevated temperature deformation. The thermomechanical procedure was executed by a deformation-dilatometer and involved double deformation processes with 25% strain at a 0.25 s⁻¹ strain rate at 900, 925, 950, and 1000 °C. The softening ratios, reflecting the competition between recrystallization and precipitation, were evaluated. The results indicated that both steels showed better softening resistance at 900 °C than at other temperatures. However, the softening ratio of 0.03 wt% Nb-containing steel (Steel 3N) rose after 100 s at 900 °C, while 0.02 wt% Nb-containing steel (Steel 2N) maintained a low softening ratio within 300 s at 900 °C, indicating that Steel 3N was relatively non-durable. A microstructural characterization showed that in the Steel 3N sample deformed at 900 °C, recrystallization occurred more strongly than for Steel 2N after a 1000 s holding time. A follow-up analysis then showed that Steel 3N treated at 900 °C revealed a faster coarsening of the carbides than Steel 2N even in the early stage of precipitation, evidencing that Steel 2N exhibited a lower softening resistance at 900 °C. Full article

Prenucleation refers to the phenomenon of atomic ordering in the liquid adjacent to a liquid/solid interface at temperatures above its nucleation temperature. It produces a precursor for heterogeneous nucleation in the liquid and thus has a strong influence on the nucleation process. Oxide particles, including magnesia, spinel, and alumina, are inevitably formed in the liquid during liquid–metal handling and casting. They may act as nucleation sites for potential grain refinement. Knowledge about prenucleation at liquid–metal/oxide (M(l)/oxide) interfaces is important for an understanding of heterogeneous nucleation during casting. Here, we present an overview of the recent studies on the prenucleation at the M(l)/oxide interfaces using ab initio molecular dynamics simulation techniques. We observed a wide variety of interfacial chemistry and identified the formation of an ordered metal layer terminating the oxide substrates, such as MgO{1 1 1} (denoting MgO with {1 1 1} surface termination), α-Al₂O₃{0 0 0 1}, MgAl₂O₄{1 1 1} and γ-Al₂O₃{1 1 1} in liquid light metals. The terminating metal atoms are positively charged and form topologically rough layers, which strongly impact the prenucleation at the interfaces. We suggest modification of nucleation potency of the substrate surfaces via elemental segregation to manipulate the solidification processes. This is demonstrated by the segregation of La atoms at the Al(l)/γ-Al₂O₃ interfaces. Full article

The melting temperature and viscosity of magnesium reduction slag were calculated by using Factsage thermodynamic software. The composition range of the magnesium-slag-based dephosphorizing agent was analyzed by drawing a multiphase diagram of the slag system. The Box–Behnken high-temperature dephosphorization experiment was designed to study the effect of different composition of magnesium-slag-based dephosphorizers on the dephosphorization rate of the steelmaking process. The results show that magnesium slag can be used as a slag-forming agent for smelting low-silicon hot metal to promote slagging, and the effect of each factor on the phosphorus removal rate is ranked, and the results are ω(Fe₂O₃) > basicity > ω(Al₂O₃): ω(Al₂O₃) has no significant effect on the rate of phosphorus removal. When the basicity was 2.8, ω(Fe₂O₃) was 25.94%, ω(Al₂O₃) was 6.73%, and ω(MgO) was 6%, the dephosphorization rate reached a maximum of 96.7%, and the error was experimentally verified to be 2.6% from the predicted value, indicating that the model can be optimized to determine the best magnesium-slag-based dephosphorization agent and has a good prediction of dephosphorization effect. Full article

The microstructure and mechanical properties of X70 pipeline steel with a ferrite/martensite dual-phase microstructure produced by thermo-mechanical controlled processing were investigated by tensile tests, Charpy V-notched (CVN) impact tests, drop-weight tear tests, guided-bend tests, scanning electron microscopy and transmission electron microscopy combined with thermodynamic simulation analysis. All the mechanical properties met the strength, ductility, toughness and deformability properties requirements of X70 grade pipeline steel with strain-based design. The shear fracture area and absorbed energy of CVN at −10 °C were >97% and >205 J in base metal (BM), weld metal (WM) and heat affected zone (HAZ) with low transition temperature, indicating adequate resistance to propagating fracture. The microstructure of WM was mainly intragranular acicular ferrite that can guarantee high strength, toughness and over matching requirements of the welded joint. Because of being exposed to successive heat inputs, the ferrite plus martensite/bainite microstructure of BM was heated between A_c1 and T_s forming the HAZ. However, a high CVN impact toughness of 345 J at −10 °C in HAZ was obtained, which indicated that the excellent mechanical properties of BM would not be seriously deteriorated during the welding thermal cycles with the reasonable addition of Ti and Nb. Full article

This paper proposes a pyrometallurgical recycling method for end-of-life NdFeB magnets by oxidizing them in air and subsequently smelting them. The smelting process enabled the recovery of rare earth elements (REEs), producing a new reach concentrate separating the iron as a metallic phase. From the products of smelting, the metallic phase showed a maximum Fe content of 92.3 wt.%, while the slag phase showed a maximum total REE (Nd, Pr, and Dy) content of 47.47 wt.%, both at a smelting temperature of 1500 °C. ICE-OES and XRD analysis were conducted on both phases, and results showed that the metal phase consists mainly of Fe and Fe₃C while the slag phase consists of the RE-oxides, leftover Fe₂O_3, and a mixture of Fe₆Nd_4. The obtained slag concentrate based on the oxides of rare earth elements is suitable for further pyrometallurgical or hydrometallurgical treatment in order to obtain rare earth elements. Full article

Fe-Ni-Cr austenitic alloys are widely used in hydrogen environments as structural materials. Their weld normally shows higher hydrogen-embrittlement sensitivity than the base metal, endangering large-scale applications. Herein, by using electron microscopy and numerical calculations, the influence of applied load on the fracture mode of hydrogen-embrittled JBK-75 alloy weldment is revealed and correlated with a competition between hydrogen-prompted intergranular decohesion (HPID) and hydrogen-enhanced localized plasticity (HELP). Therefore, independent of the load levels, the weld featuring a lower strength and smaller grain sizes is always more vulnerable to hydrogen embrittlement than the base metal. Full article

In this study, we used 0.2C-1.7Si-1.9Mn wt% cold-rolled sheet as the experimental material to prepare the Q&P sample with blocky microstructures and the QQ&P sample with lath-shaped microstructures through the Q&P and QQ&P processes, respectively. The partitioning behavior of carbon and manganese in the two samples after intercritical annealing and partitioning were studied. During the intercritical annealing, the partitioning of carbon and manganese in the Q&P and the QQ&P samples occurred, resulting in the contents of carbon and manganese being significantly higher than those in the ferrite. Meanwhile, due to the migration of the ferrite–austenite interface during the formation of the austenite, the distributions of carbon and manganese in the lath-shaped and blocky austenite were both homogenous. The morphology of the microstructures had little influence on the distribution of carbon and manganese in metastable austenite during intercritical annealing. In the partitioning, the migration of the ferrite–austenite interface and diffusion of manganese can be ignored. Carbon first diffuses from the ferrite grains to the ferrite–austenite interface and then diffuses in the austenite grains. The morphology of the microstructures has a great effect on the homogenization of carbon in austenite grains. Compared with coarse blocky austenite, lath-shaped austenite can shorten the diffusion path of carbon in austenite grains and increase the homogeneity of carbon in austenite grains, thereby improving the thermal stability of lath-shaped austenite. Compared with the Q&P sample, the QQ&P sample has higher content of retained austenite (14.74% vs. 13.96%), better elongation (25.9% vs. 19.2%), and higher product of strength and elongation (27.5 GPa% vs. 24.4 GPa%). Full article

Fabrication of thick (more than 3 mm) hard coatings on Al-Mg alloys might provide better performance in terms of increased durability, wear resistance and hardness compared with the unmodified material. In this study we fabricated Al-Co-Cr-Fe-Mn-Ni high-entropy alloy coating by wire-arc additive manufacturing onto AA5083 substrate. The aim of this study is to investigate the microstructure and mechanical properties of the coating and its influence on the substrate. Scanning electron microscopy and transmission electron microscopy were used to characterize the microstructure and elemental composition of the obtained coating. Microhardness and tribological tests were implemented to evaluate the mechanical properties. The results showed homogeneous distribution of the elements alongside the transversal direction in the coating which has the following average chemical composition: Al 8 at. %, Co 28 at. %, Cr 13 at. %, Fe 33 at. %, Mn 3 at. %, Ni 15 at. %. The wear rate of the coating decreased by ~five times comparing with the substrate, while the Vickers hardness improved by ~three times. The highest level of hardness accounting for 1010 ± 80 HV was observed in the transition zone between the coating and the substrate which might be attributed to high micro- and macrostress levels appeared in this zone. The study showed the practical applicability of wire-arc additive manufacturing method to fabricate a high-entropy alloy on Al-Mg substrate. Full article

Titanium has been one of the traditional metals used in the medical industry since 1940. This work modeled and simulated a hip-joint replacement implant using Creo 5.0 and DEFORM 3D (v11.0), respectively. Four titanium-based billets were modeled; out of four billets, three billets were coated with a specified thickness, and one was uncoated. Among the three coated billets, one billet was coated with a 500-micron and two billets coated with a 1000-micron thickness. At the end of the simulation, the coating materials formed patches on the surface of the forged parts. The coating material Ti-6Al-4V (high O₂) produced excellent mechanical properties in contrast to the CP-Ti material, which displayed low mechanical properties and did not match the core property. Hence, it was suggested to provide a bulk coating of Ti-6Al-4V (high O₂) on the billet to improve the physio-mechanical properties and biocompatibility. Four points were selected on the surface of the forged parts at different locations for identifying the property variations concerning forging time. Results found that coating thickness required more on the side surface of the billet material than on the upper and lower surfaces to enhance its properties. Full article

Microstructures and mechanical properties of Al-5Zn-2.6Mg alloys with 0.24, 0.43, and 0.91 wt.% Cu were studied and the precipitation rate and activation energy at 378, 393, and 408 K were calculated using the Arrhenius equation in this work. The aging reaction rate k increased and the precipitation activation energy E_a decreased from 25.7 to 15.0 kJ/mol. The η’ distribution density of the precipitates clearly increased with increasing Cu content. However, the size and number of coarse second phase with Fe and Mn impurities also increased, which increased the tendency for crack initiation and propagation at the grain boundary, resulting in a decrease in dimple area. The fracture morphology transformed from plastic transgranular fracture to brittle intergranular fracture and the elongation of the alloys decreased by 3.8%. The contribution of Cu content to yield strength was predominantly due to precipitation strengthening rather than grain boundary strengthening and solid solution strengthening. The tensile strength of the Al-5Zn-2.6Mg alloys with 0.91 wt.% Cu subject to peak aging at 393 K increased by 10.2%. Full article