Zn and its alloys have recently been used as a new class of biodegradable biomedical metals besides magnesium and iron alloys, owing to their moderate corrosion rate and good mechanical properties. In recent years, researchers have rigorously studied the design, processing, and degradation mechanism of Zn alloys, but their biocompatibility has not been well explored. Past research on the biocompatibility of Zn alloys focused on in vitro cytotoxicity, hemolysis, and coagulation, and only a few materials were implanted into animals for characterizing the histocompatibility. Biocompatibility involves complex local and systemic reactions, such as cells, tissues, blood, and immunity. In addition to the physical and chemical properties of the material, the biocompatibility is also affected by interactions between the material and body. In this paper, the chemical and phase compositions of degradable zinc alloys were analyzed, and the biological evaluation methods were clarified. In view of the recent studies on zinc alloy biocompatibility, future research directions were proposed.

Body-centered-cubic (bcc)-structured metals have excellent physical properties, such as high melting points, high strength and excellent creep resistance, radiation tolerance, and good compatibility with liquid metals, which are widely used in high-tech fields, such as nuclear reactors, satellites, aircraft, rockets, and engines. However, their low-temperature brittleness and ductile-to-brittle transition characteristics limit their applications. Therefore, a deep understanding of the ductile-to-brittle transition mechanism is of great significance for regulating the ductile-to-brittle transition behavior of bcc-structured metals. In this review, taking bcc-structured metals as an example, the history of the ductile-to-brittle transition investigations in bcc metals was retrospected, the main research progress on this topic was introduced, the newly developed methods to tune the ductile-to-brittle transition temperature of metals was discussed, and the key points to be focused on in the future was listed.

Mg-based hydrogen storage materials have drawn a lot of attention due to the merit of high hydrogen storage density, earth-abundant resources, and environmental friendliness. However, the slow kinetics, high hydrogen absorption/desorption temperature, and poor cycling stability of Mg-based hydrogen storage materials prevent them from being used on a large scale. The developments of new alloys, nano-structure control, catalytic modification, and multiphase composites, among other things, have made significant progress in Mg-based hydrogen storage materials in recent years. However, challenges still exist, such as high hydrogen storage capacity, moderate adsorption/desorption temperature, rapid reaction rate, and long cycling life. In this review paper, the types of hydrogen storage phases and their interface in Mg-based materials, and the control methods of their microstructure/interface characteristics are systematically summarized. The mechanism of the hydrogen storage phase, microstructure, and surface/interface modifications on the improved thermal/kinetic performance of hydrogen storage are highlighted. This review concludes with an outlook and prospects on the challenge of designing Mg-based hydrogen storage materials by controlling the hydrogen storage phase and the corresponding interface.

This paper briefly reviews the progress on high-temperature oxidation mechanisms of pure Mg and Mg alloys, the thermodynamics and kinetics of high-temperature oxidation of Mg alloys, and the antioxidation mechanism of Mg alloys. The potential of applying advanced characterization techniques in studying the high-temperature oxidation of Mg alloys is envisaged. Finally, the development trends of the oxidation-resistant Mg alloy are also summarized. The main viewpoints are as follows: The protection of magnesium alloys at high temperatures is provided by the formation of a continuous, dense oxide scale that is a specific thickness and prevents the outward diffusion of magnesium vapor and the inward diffusion of oxygen; the oxidation resistance of Mg alloys is usually closely related to the thermal stability of the second phases; when the trace alloy elements are not enough to form the corresponding surface oxide scale, the oxidation resistance can be improved by creating a substitutional solid solution and using the reactive element effect; the size of the oxide grain size decreases and then enhances the oxidation resistance once the surface active elements is enriched on the surface of the alloys; the selective oxidation and synergistic effect of alloying elements are critical to the oxidation resistance of Mg alloys; the addition of nano or microparticles into the Mg alloys improve the high-temperature oxidation resistance of the Mg alloy by reducing the size of specific oxidation sensitive regions. In the future, the research on the high-temperature oxidation of Mg alloys can be based on the following aspects: Investigating the processes and nature of the oxidation resistance of Mg alloys using cutting-edge characterization techniques; constructing the underlying connections between the alloying elements and the oxide scale grain size and mechanical properties; designing and optimizing multi-alloying element composition systems.

Nickel-based superalloys have been widely used in aero engines and gas turbines because of their excellent high-temperature strength and exceptional oxidation resistance. The oxidation resistance is obtained using the thermal barrier coatings and alloying elements. In the previous investigations, the oxidation time of the nickel-based superalloys has been focused on hundreds of hours. However, in practice, the superalloys last far longer. This study investigated the superalloy DZ445's oxidation behavior at 900^oC for 300-2600 h. An oxidation film with a four-layer structure is formed after oxidation at 900^oC for 500 h and above. The outermost layer is primarily composed of NiCr₂O₄, Cr₂O₃, and TiO₂. The subouter layer consists of CrTaO₄ and TiO₂, and the subinner layer consists of Al₂O₃, NiCr₂O₄, and NiO. The innermost layer is primarily Al₂O₃. The appearances of the subouter layer and subinner layer greatly reduce the oxidation rate of the alloy, which is represented by the dramatic increase in the oxidation kinetics equation exponent and a sharp reduction of the oxidation rate constant. The formation of subouter layer changes the oxidation mechanism from outward diffusion of alloy elements to O-inward diffusion. When the subinner layer is formed, the oxidation behavior is controlled using the outward diffusion of Ni and Cr and the O-inward diffusion. The multilayer structure gave the alloy an excellent oxidation resistance capacity.

With the rapid development of electric, electronics, and military industries, there is an urgent demand for high-performance electrical steel. Non-oriented 6.5%Si electrical steel is an advanced soft magnetic material that exhibits excellent high-frequency soft magnetic properties, such as low iron loss, high magnetic permeability, and near-zero magnetostriction, which attracts considerable attention and has broad application prospects in the high-frequency field. Microalloying of rare earth elements, including Ce, La, and Y, is known to improve the ductility of 6.5%Si electrical steel. However, there are relatively few studies on the enhancement mechanism of medium-temperature plasticity of 6.5%Si electrical steel by addition of Y. In this study, the effect of Y on the solidification microstructure, ordered phase, warm compression behavior, and softening mechanism of non-oriented 6.5%Si electrical steel was investigated by EPMA, EBSD, XRD, TEM, and hot compressive test. The results indicated that the addition of 0.017% and 0.15% of Y led to the formation of high-melting-point Y₂O₃ + Y₂O₂S/Y₂O₂S-YP compounds in the melt which effectively promoted heterogeneous nucleation. At the end of the solidification process, the interdendritic rare-earth compounds were identified as Y₂Fe₁₄Si₃ and the solidification microstructure was obviously refined. In addition, with the increasing Y content, the ordered degree of the matrix decreased. The compression test at 500^oC indicated that the deformation mechanisms of all the specimens were dominated by a dislocation slip. The critical strain corresponding to the peak stress of the specimens doped with Y decreased. The advancement of the work softening stage and reduction in the following work hardening rate suggested that the dynamic softening effect was enhanced in the specimens doped with Y. After deformation, the matrix was in a disordered state, however, the dislocation density in the matrix was directly proportional to the Y content. Eventually, the primary reason for the enhancement of the dynamic softening effect was attributed to the low ordered degree and high deformation-induced disordering of the matrix by addition of Y.

The production of quenching and partitioning (Q&P) steel using hot-rolled steel instead of cold-rolled steel can significantly reduce the manufacturing process time and cost. However, the initial microstructures of hot-rolled and cold-rolled steels are different, which affect the microstructures and mechanical properties of Q&P steel. Because most studies used Q&P steel prepared from cold-rolled steel, the microstructures and mechanical properties of Q&P steel prepared from hot-rolled steel are unclear. This study examines the microstructures and mechanical properties of Q&P Si-Mn steel prepared from hot-rolled steel as a function of the austenitizing temperature. The results showed that the ferrite in the Q&P Si-Mn steel produced from the hot-rolled steel had lath-type and blocky-type morphologies. The observed ferrite morphology could influence the morphology of the adjacent retained austenite. The lath-type and blocky-type ferrite surrounding the retained austenite was mainly observed as the thin lath and blocky types, respectively. The ferrite and retained austenite contents decreased with increasing austenitizing temperature. In addition, the corresponding yield and tensile strengths increased gradually with a concomitant decrease in elongation and the product of strength and elongation. When the austenitizing temperature was 810^oC, the product of strength and elongation of the Q&P Si-Mn steels produced from hot-rolled steel reached 28.36 GPa·%, which was approximately 36% higher than that of Q&P980 produced industrially from cold-rolled steel. The higher product of strength and elongation of Q&P Si-Mn steel produced from hot-rolled steel may be related to the different morphologies of ferrite, which might control the morphology and stability of the adjacent retained austenite. These experimental results could provide a theoretical basis for preparing Q&P steel from hot-rolled steel instead of cold-rolled steel.

The Pt-Al coating is a vital section of aero-engine power blades that can improve the operating temperature of the blade. The blade is subjected to axial tensile stress during operation. Both the oxidation of the Pt-Al coating and the microstructure evolution caused by the element diffusion between the coating and the matrix at high temperatures affect the service performance of the blade. However, the specific mechanisms remain unclear. In this work the effect of Pt-Al coating on the tensile properties of a DD413 alloy was studied. SEM and TEM were used to compare the tensile properties of the uncoated and Pt-Al-coated samples, respectively, at 760 and 980^oC. Lower yield strength was detected in Pt-Al-coated samples than that in uncoated samples at 760 and 980^oC. The different crack initiation modes and deformation mechanisms of Pt-Al coating at 760 and 980^oC mainly result from the ductile to brittle transition temperature (DBTT). At high temperatures, the transition from β to γ′ is conducive to the dislocation slip, which leads to the plastic deformation of the Pt-Al coating. The increase in the tensile strength of the Pt-Al layer above DBTT can be attributed to the solidified solution-strengthening effect of Pt in β-NiAl.

Based on the actual production data of the plate mill of Xingcheng Special Steel, two machine learning methods for predicting deformation resistance are proposed to improve prediction accuracy. The first is a multi-steel deformation resistance model and modeling method that is combined with an extreme learning machine (ELM) and a traditional mathematical model, and the second is a deformation resistance model and modeling method that is based on the TensorFlow deep learning framework. Method one: The structural form of the original deformation resistance model was improved by referring to the Zhou Jihua-Guan Kezhi deformation resistance model, and the reference deformation resistances of representative steel grades of low alloy steel, alloy steel, and high alloy steel were calculated. The influence coefficient of deformation parameters independent of steel grade was calculated using nonlinear regression. The ELM neural network algorithm was presented, and neural network parameters were optimized using grey correlation analysis and cross-validation. To reduce the residual error of ELM prediction, the prediction results were smoothed using linear interpolation and then combined with the traditional mathematical model to obtain the deformation resistance. Method two: Based on deep learning technology, two types of deep neural networks with different structures were built and combined with the mechanism. To improve the generalizability and stability of the model, the mini-batch and RMSprop optimization algorithms were used in conjunction with batch normalization (BN) and early stopping regularization strategies. Finally, deformation resistance prediction models for roughing mill (RM) and finishing mill (FM) were developed respectively in conjunction with the process characteristics to improve model accuracy. The results showed that the deformation resistance prediction using deep learning has high prediction accuracy. Offline analysis indicated that the mean absolute percentage error decreased from 9.27% of the original model to an average of 2.59%. The online application demonstrated that the ratio of rolling force prediction accuracy within 10% relative error increased from 72.31% to an average of 90.24%, raising the technological level of onsite production.