Abstract: A novel Ti-N-O composite was prepared by powder nitriding/ oxynitriding combined with Spark-plasma Sintering（SPS）method. The effects of N/O on the microstructure and mechanical properties of Ti-N-O alloy were systematically studied. The results showed that the addition of N/O elements significantly improved the yield strength and the hardness of commercially pure titanium(cp-Ti). And the O element played a leading role in regulating the microstructure and morphology of Ti-N-O alloy. With the addition of O element, the microstructure showed equiaxed structure, and the characterization showed that this region is O-enriched region, and a small amount of nano-TiO2 particles appeared in the alloy, which together led to the change of the microstructure. At the same time, more large-angle grain boundaries were generated in the Ti-N-O alloy.

Abstract: Oxide dispersion strengthened (ODS) steels are among the most promising candidate structural materials for fusion and Generation-IV (Gen-IV) fission reactors, but the ductility of ODS steels is inferior to its strength properties. Therefore, we investigate void nucleation, considered as the first step of ductile damage in metal, using molecular dynamics simulations. Given that the materials are subjected to extremely complex stress states within the reactor, we present the void nucleation process of 1-4 nm Y2O3 nanoclusters in bcc iron during uniaxial, biaxial, and triaxial tensile deformation. We find that the void nucleation process is divided into two stages depending on whether the dislocations are emitted. Void nucleation occurs at smaller strain in biaxial and triaxial tensile deformation in comparation to uniaxial tensile deformation. Increasing the size of clusters results in a smaller strain for void nucleation. The influence of 1nm clusters on the process of void nucleation is slight, and the void nucleation process of 1nm cluster cases is similar to that of pure iron. In addition, void nucleation is affected by both stress and strain concentration around the clusters, and the voids grow firstly in the areas of high stress triaxiality.

Abstract: Characterizing powder feedstock is crucial for ensuring the quality and reliability of parts produced through metal additive manufacturing (AM). The morphology of particles impacts flowability, packing density, and spreadability of powders, affecting productivity and part quality. A new methodology has been developed to classify particle morphological features in AM powder feedstocks, such as spherical or elongated shapes, and the presence of satellites and facets. This approach uses multiple descriptors for quantitative evaluation. The results from shape descriptors can vary based on image resolution, grey/colour thresholding, and software algorithms. There are various commercial systems available for characterizing particle shape, some of which use images taken of static particles, while others use images of particles in motion. This diversity can lead to differences in powder characterization across laboratories with different equipment and methods. This paper compares results from a particle classification approach using two software programs that work with metallographic images with those from an automated static particle analyzer. While traditional methods offer higher resolution and precision, the study shows that automated systems can achieve similar particle shape classification using different shape descriptors and thresholds.

Abstract: Magnesium alloys are important lightweight structural materials in engineering applications. However, conventional single-phase hexagonal close-packed (HCP) magnesium alloys exhibit poor plastic deformability and insufficient strength at room temperature, which limits their widespread application. In contrast, Mg-Sc alloys with a dual-phase structure (HCP + BCC) demonstrate significantly improved plastic deformability at room temperature compared to single-phase HCP magnesium alloys. In this work, the deformation behavior of dual-phase Mg-19.2 at.% Sc alloy was investigated, revealing its deformation characteristics and multiscale strengthening mechanisms. With increasing heat treatment temperature, the volume fraction of the β phase gradually increased. When the β phase fraction reached 80%, the alloy exhibited the optimal combination of strength and plasticity (ultimate tensile strength: 329 MPa, elongation: 20.5 %). Microstructural analysis reveals that the plastic incompatibility between α/β phases results in significant heterogeneous deformation-induced (HDI) strengthening. The unique bimodal grain size distribution, with the average grain size of the α phase significantly smaller than that of the β phase, further amplified the HDI strengthening contribution by enhancing the "hard phase harder, soft phase softer" heterostructure effect. This study provides new theoretical guidance for designing high-performance dual-phase magnesium alloys from the perspective of multiphase interface engineering.

Abstract:

This study developed a new heat treatment method, normalizing & stress relief (N.S.R), to increase productivity compared to spheroidizing annealing (S.A). The influence of different microstructures resulting from these heat treatments was investigated in cold-forged steel. Despite a shorter heat treatment time, the mechanical properties of the N.S.R alloy were found to be similar to those of the S.A alloy. The factors influencing the mechanical properties of the experimental alloys were analyzed using the Hall-Petch equation, and the predicted values closely matched the measured strength of hy-per-eutectoid steels. The primary factors affecting mechanical properties were micro-structure and dislocation density. In the case of the S.A alloy, the microstructure exhibited lower strength due to the spherical cementite structure. In contrast, the N.S.R alloy had lower strength because of a reduced dislocation density. This was achieved by stress-relief heat treatment below the A1 temperature after phase transformation. Based on the mechanical properties, cold forging simulations showed that the effective stress during cold forging of the N.S.R alloy was similar to that of the S.A alloy.

Abstract: In the present work, the effect of different casting processes on the microstructure and creep properties of the second-generation single-crystal superalloy DD419 was investigated. Under conventional production conditions and a contour-suited thermal insulation method, single crystal rods of types A and B were fabricated, respectively. In comparison to rods A, the solidification process of rods B featured a 1.6-fold increase in the temperature gradient and a 32% reduction in primary dendrite spacing. The γ/γ’ eutectic in the as-cast microstructure, the residual eutectic phase, and porosity after heat treatment were also significantly reduced, resulting in the improved homogeneity of the single crystal castings. Under the testing conditions of 850°C/650MPa and 1050°C/190MPa, the stress rupture life of sample B was enhanced by 25% and 5.2%, respectively, compared to sample A. Therefore, due to dendrite structure refinement, the stress rupture life of the superalloy was evidently improved, especially at medium temperature.

Abstract: The Mg-Y-Zn magnesium alloy system is known for the presence of Long-Period Stacking Ordered (LPSO) phases that improves strength and ductility with minimal amounts of alloying elements. Even better improvements are associated with the specific microstructure known as the Mille-Feuille structure (MFS) that can occur in this alloy as well after proper heat treatment. This study systematically compares the traditional ingot metallurgy method with the Bridgman method (slow cooling), coupled with diverse heat treatments and extrusion process. Microscopic analyses reveal variations in the presence of LPSO phases, Mille-Feuille structure, and especially grain size, leading to divergent mechanical and corrosion properties. The Bridgman approach surprisingly stands out, ensuring superior mechanical properties due to kink and texture strengthening.

Abstract: Understanding mold flux crystallization is essential for evaluating heat transfer during steel casting. In casting, the mold gap's complexity raises questions about the ideal testing method and nucleation type—heterogeneous or homogeneous. This study examines how crucible materials influence mold flux crystallization, focusing on the wetting behaviors of platinum and graphite with mold flux. Confocal laser scanning microscopy (CLSM) was employed to observe in-situ nucleation, and differential scanning calorimetry (DSC) was used under non-isothermal conditions across cooling rates (5–30°C/min) for the flux sample to determine the crystallization temperatures. Results showed significantly lower crystallization temperatures in graphite crucibles versus platinum, with similar trends for synthetic slag and Li2SO4, validated through experimental DSC data and Factsage® simulations. X-ray diffraction (XRD) and scanning electron microscopy- energy dispersive X-ray spectroscopy (SEM-EDS) were utilized to identify crystal phases and interactions between the flux and graphite wall. Graphite’s non-wetting characteristics hindered nucleation, requiring greater undercooling, while platinum’s superior wetting properties facilitated nucleation by lowering surface energy and the free energy barriers. These findings highlight the influence of crucible materials on nucleation behavior, providing valuable insights for refining mold flux testing methodologies and, ultimately, advancing the understanding of nucleation mechanisms during solidification in the casting process.

Abstract: High-entropy alloys (HEAs) have emerged as a novel class of materials that exhibit a wide range of desirable properties making them a focal point for research and potential applications across various industries. The complexity and variability in the compositions of HEAs pose a significant change in predicting their phases, which is crucial for determining their applicability and performance in specific applications. Accurate phase prediction is essential for determining the ideal combination of elements required to design HEAs with targeted properties. This study proposes a machine learning (ML) based approach to predict the phase structure of HEAs utilizing experimental data containing features derived from the chemical composition and corresponding phases. A Boolean vector technique was employed to represent the presence or absence of multiple phase combinations enhancing the model’s ability to accurately capture complex phase structures. Four robust ML algorithms consisting of support vector machine (SVM), k-nearest neighbors (KNN), random forest (RF) and neural network (NN), were employed to develop models capable of classifying the phases of HEAs. The performance of these models was rigorously evaluated through testing on unseen data samples. The findings revealed that both NN and KNN demonstrate superior performance achieving a remarkable test accuracy of 84.85%. This study underscores the potential of ML as an effective tool for predicting the phases of HEAs, offering a new avenue for more innovative approaches to material design and discovery in the future.

Abstract: This study explores the mechanical and corrosion properties of yttria-reinforced 316L stainless steel. Powder precursor materials were prepared using mechanical alloying. Varying yttria (Y₂O₃) content (1, 3, and 5 wt%) was used to assess its impact on the steel’s properties. X-ray diffraction and scanning electron microscopy confirmed the successful dispersion of Y₂O₃ within the matrix, with the formation of chromium carbides during spark plasma sintering (SPS). The mechanical properties, including hardness and compressive yield strength, improved with increasing Y₂O₃ content, with the highest strength observed in the 316L-5Y₂O₃ sample. However, corrosion resistance decreased with higher yttria concentrations. The 3 wt% Y₂O₃ sample exhibited the highest corrosion rate due to localized corrosion in areas enriched with oxide particles and chromium carbides. Electrochemical testing revealed that carbide formation and Cr-depleted regions from SPS processing contributed to the corrosion behavior. These findings suggest that while yttria reinforcement enhances mechanical strength, optimizing Y₂O₃ content and processing methods is crucial to balance both mechanical and corrosion performance in ODS 316L stainless steel.

Abstract: The friction between the roll and the rolled piece is the main force of plate-strip rolling, and the friction condition of the roll gap seriously affects the surface quality of the plate-strip. Therefore, the friction condition is an important boundary condition in the analysis of plate-strip rolling deformation. The finite element model of SUS304 foil rolling was established by crystal plasticity finite element method, and the accuracy of the rolling model was verified by comparing the measured grain orientation of foil after rolling with the simulation results. Based on the above model, the effects of friction conditions on rolling force, contact pressure and friction stress, slip system motion state and grain orientation of rolled SUS304 foil strip were analyzed. The results show that with the increase of friction coefficient, the length of the forward slip zone increases, the surplus frictional force increases, and the contact pressure and friction stress of the upper and lower rolls in the rolling deformation zone increase slightly. The change of friction coefficient has a great influence on the shear slip of the surface layer of the foil strip, which significantly affects the motion state of the activated slip system at the upper and lower surface positions of the foil strip, significantly improves the shear strain of the activated slip system at the upper and lower surface positions, and increases the dispersion degree of the grains in the upper and lower surface layers around the ND direction.

Abstract:

The direct hot modification and then preparation of qualified building materials from molten slag have gained significant attention at present due to its characteristics to save energy and reduce CO2 emissions. Molten silicomanganese slag discharged at 1500-1600 ℃ with high content of SiO2 and Al2O3 (above 50 mass%) is suitable for preparation of casting stone. For ensuring a qualified casting stone, the study focused on the improvement of crystallization properties and fluidity of molten silicomanganese slag by modification of its composition, crystallization, structure, viscosity of raw slag and two modified slags, and physical properties of their final cast stone was compared and discussed. The results showed that after modified by addition of 10 mass% chromite and serpentine or 20 mass% ferrochrome slag into silicomanganese slag, both crystallization ability and fluidity of the molten slag were improved simultaneously. Augite and spinel precipitated in the modified slag compared with glass phase in the raw slag. The precipitation of spinel on the one hand acted as a nucleation agent, dynamically promoting the formation of augite, and on the other hand, increased the proportion of SiO2 and its polymerization of [SiO4] structural units in the residual liquid slag, further promoting the generation of augite in composition and structure. The gradual precipitation of crystals effectively mitigates sudden viscosity fluctuations resulting from crystallization, contributing to a smooth casting process for molten slag. Both cast stone from the modified slag exhibited qualified physical properties, compared with the broken glass from the raw slag. It indicates a feasibility for a simple and low-cost modification during discharging process of molten silicomanganese slag by blending 10 mass% cold modifiers or 20 mass% molten ferrochrome slag into it.

Abstract:

First-principles calculations are performed to examine the physical features of full Heusler ln2MnW. The WIEN2K code is utilized with the variety of approximations, including the GGA and GGA + U, to examine the structural, electronic, and magnetic properties. The unit cell is optimized to achieve the ground state energy level. The calculated ΔH for In2MnW is -0.189 eV. This negative ΔH value signifies the thermodynamic stability of the compound. The metallic behavior of the investigated compound is confirmed by the calculated band structure (BS) with both potentials. These potentials are also used to calculate the total density of the state, which confirm their metallic nature. Total magnetic moment value is recorded as 4.3 µB while addition of U parameter slightly enhances its value to 4.4 µB. These studied properties indicate that ln2MnW has a metallic ferromagnetic character and is ideally appropriate for the usage of mass storage devices as a ferromagnetic material.

Abstract: A simple short-flow thermo-mechanical treatment named L-ITMT (consisting of three steps: solution, warm deformation, and solution) were implemented in ultra-high strength Al-10.0Zn-2.7Mg-2.3Cu alloy to study the Deformation degree on the particle distribution, resolubility, microstructure evolution, recrystallization mechanism, formation and development of deformation bonds and mechanical property. Increasing the rolling deformation during the L-ITMT process can effectively break up the second phase at the grain boundary and promote its dissolution, which is beneficial to aging precipitation strengthening and improves the strength of the alloy. The dominant mechanism changes from recovery to recrystallization when the strain reaches 0.92. As the strain increases, the deformation band becomes flatter and eventually becomes nearly parallel to the RD direction, promoting the occurrence of geometric recrystallization or continuous recrystallization (CRX). Under high strain conditions, the formation mechanisms of recrystallized grains include discontinuous recrystallization (DRX), CRX and particle stimulated nucleation (PSN), but the main contributions to the formation of large-area fine-grained bands are CRX and PSN. The results showed that as the deformation degree increased from 10% to 80%, the improvement of solid solubility and grain refinement in the short-flow TMT process increased the ultimate tensile strength (701 MPa), yield strength (658 MPa), and elongation (11.3%) of the alloy by 15.7%, 10.8%, and 842%, respectively. This shows that the short-process L-ITMT process has a synergistic effect in significantly improving the plasticity and maintaining the strength of the ultra-high strength Al-Zn-Mg-Cu alloy.

Abstract: 316L stainless steel was prepared via selective laser melting (SLM), and the effect of heat treatment on microstructure, density, microhardness and wear resistance were studied. The results show that specimens exhibit anisotropy in microstructure, density, microhardness and wear resistance, the microhardness and wear resistance of XOY plane is higher and better than XOZ plane. X-Ray diffraction (XRD) analysis indicated that specimens exhibit FCC austenite phase, no new phase is found after heat treated, indicating that it has good thermal stability. Microstructure of SLM 316L exhibits obvious melt pools composed of columnar crystals and cellular crystals, some nano silicon oxides adhere to the surface of the cellular crystals. SLM 316L presents as intersecting melt pools on the XOY plane and fish-scale-like melt pools on the XOZ plane. After heat treated, the melt boundaries annihilate and recrystallization of the specimens lead to the coarsening of the microstructure. Microhardness results show the microhardness decrease after heat treated and the specimen with the lowest decrease in microhardness after solution+aging treatment. The friction and wear tests results reveal the specimen after solution+aging treatment has the lowest friction coefficient and smallest wear loss, exhibiting the best wear resistance.

Abstract: Effect of electroless deposited on (non-anodized and anodized) Al 1050 of: monolayer Ce2O3+Ce2O4; consecutive deposited be-layer Ce2O3+Ce2O4/Ca5(PO4)3OH or consecutive deposited be-layer Ce2O3+CeO2/(AlPO4+AlOOH+CePO4) systems on the indentation modulus (ЕIT) and hardness (HIT), as well as their corrosion-protective ability were investigated. For structural, chemical, electrochemical and mechanical characterization of the investigated systems following methods were used: scanning electron microscopy (SEM), energy dispersive X-rays analysis (EDXS), X-ray photoelectron spectroscopy (XPS), polarization resistance (Rp), corrosion rate (CR) analysis, and Nanoindentation. It was found that the HIT and ЕIT of the coatings deposited on an anodized aluminum substrate were much higher than those deposited on a non-anodized alumi-num substrate. It is established a specific influence of the morphology and chemical composition of formed conversion layers on HIT and EIT as well as as on the improvement of corrosion-protective effect of these layers. The obtained results are valuable, since there are no data on the mechanical properties of such coatings in the literature up to this point.

Abstract: In this study, a (TiB + TiC + Y2O3)/α-Ti composites was prepared by induction skull melting to investigate its creep behavior and microstructure evolution under different temperatures and stresses. The results show that the microstructure of the composites in the as-cast state is a basket-weave structure, with the main phase composition is α lamella, containing a small amount of β phase and equiaxed α phase. The creep life of the composites decreases significantly when the temperature is increased from 650 °C to 700 °C, and the steady-state creep rate is increased by 1-2 orders of magnitude. The creep stress exponent at 650 °C and 700 °C is 2.92 and 2.96, respectively, and the creep mechanism of the titanium matrix composites are dominated by dislocation movement. TiB and TiC exhibit synergistic strengthening effects, and Y2O3 remains stable during creep. The reinforcements strengthen the composites by impeding the dislocation movement. The accelerated dissolution of β phase is one of the major reasons for the decrease of creep properties of composites with increasing temperature and stress. Silicide precipitation was observed near the reinforcements and dissolved β-Ti, mainly in elliptical or short rod shapes, which pins dislocations and improves the creep performance of the composites.

Abstract: Optical microscope (OM), energy dispersive spectrometer (EDS), electron backscatter diffractometer (EBSD), electrochemical test, and transmission electron microscope (TEM) were employed to conduct interface microstructure observation and cladding corrosion resistance analysis on 304 SS/CS clad plates that have four different reduction ratios. The increase in rolling reduction ratio leads to larger grain size, gradually refined microstructure, and a decreased thickness of the interfacial martensite area. As the concentration disparity of the C element between carbon steel (CS) and 304 stainless steel (SS) is small, no evident carburization layer and decarburization layer can be detected. The ferrite microstructure on the CS side has a greater stress distribution, a greater local orientation deviation, and deformed grains are dominant. Austenite undergoes strain-induced martensitic transformation with the transformation mechanism of γ→twinning→a'-martensite. The martensite microstructure within the interface region grows in the direction of the interior of austenite grains. The reduction ratio increases sharply, leading to an increase in dislocation density, which promotes the nucleation, growth, and precipitation of carbides and seriously reduces the corrosion resistance of the cladding. Subsequently, the reduction ratio keeps on increasing. However, the degree of change in the reduction ratio diminishes. High temperature promotes the dissolution of carbides and improves the corrosion resistance. From this, it can be understood that by applying the process conditions of raising the reduction ratio and keeping a high temperature at the carbide dissolution temperature, a clad plate that has excellent interface bonding and remarkable corrosion resistance can be acquired.

Abstract: Metal hydride hydrogen compressors have attracted great attention due to their reliable safety, environmental friendliness, and the absence of vibration and noise. Herein, the effects of Ti substitution for Zr on the crystal structure and hydrogen comprehensive performance of Ti0.92+xZr0.1-xCr1.0Mn0.6Fe0.4 (x = 0, 0.01, 0.02, 0.03) are investigated systematically. Among the investigated alloys, the Ti0.94Zr0.08Cr1.0Mn0.6Fe0.4 alloy can be considered as a promising candidate for application with a hydrogen capacity of 1.82 wt.% under 9 MPa at -10 °C. Meanwhile, it exhibits excellent hydrogen absorption kinetic performance, reaching 1.655 wt.% in 5 min. The desorption pressure at 83.9 °C is determined to be 25 MPa by Van't Hoff fitting plots, which fulfills the requirement of producing over 25 MPa hydrogen pressure in water-bath environments with a high compression ratio of 3.08. The Ti0.94Zr0.08Cr1.0Mn0.6Fe0.4 alloy is very promising for hydrogen refueling applications in long tube trailers and low-pressure gas cylinders.

Abstract: The AlCoCrFeNi high entropy alloys are a novel structural material with wide application prospects. In order to investigate the influence of Al and Cr elements on the structure and properties of the alloys, AlxCr1-xCoFeNi (x=0.1, 0.2; 0.3, 0.4, 0.5) HEAs were prepared by mechanical alloying and spark plasma sintering. The microstructure and properties of the AlxCr1-xCoFeNi were analysed using XRD, SEM, EDS, electrochemical workstations, hardness measurement, friction and wear measurement, and room temperature compression measurement. The hardness and friction measurement results demonstrate that when x = 0.1, the crystal structure of Al0.1Cr0.9CoFeNi is composed of dual FCC phases and a trace of σ phase. With the increment of Al content, part of the FCC phase is transformed into BCC phase. When x=0.2~0.5, the alloy is composed of dual FCC phases, BCC phase and a trace σ phase. The Al0.5Cr0.5CoFeNi alloy exhibits the most favourable corrosion resistance, with a self-corrosion voltage of 0.202 V in a 3.5 wt.% NaCl solution. The hardness of alloy increases with the increasing of Al content. The Al0.5Cr0.5CoFeNi alloy exhibits the highest hardness value of 412.6 HV. At the initial stage of friction measurement, the wear mechanism of AlxCr1-xCoFeNi was adhesive wear. As the test time increased, oxide layers began to form on the surface of the alloy, resulting in a gradual increase in the coefficient of friction. At this stage, the wear mechanism was characterised by both adhesive and abrasive wear. Once the oxide layers and the wear processes reached dynamic equilibrium, the friction coefficient stabilised, and the wear mechanism transitioned to abrasive wear. Once the oxide layer and the wear process have reached dynamic equilibrium, the friction coefficient tends to stabilise gradually, and the wear mechanism is changed to abrasive wear. Al0.1Cr0.9CoFeNi has the smallest coefficient of friction of 0.513. Al0.5Cr0.5CoFeNi had the longest compression plateau and the greatest compression strain (59.7%) in the compression tests at room temperature.