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To improve the surface properties of low-density wood, poplar wood was functionalized by laminating Al2O3impregnated paper onto poplar wood (Populus tomentosa Carr.) via unilateral surface compression. Bonding strength between Al2O3impregnated paper and wood reached up to 3.08 MPa, meeting commercial grade I requirements for impregnated paper laminated wood flooring. A cross-linked structure between Al2O3impregnated paper and wood was formed without visible cracks or other defects. Density of the functionalized wood surface increased remarkably and the surface hardness was significantly improved, surpassing that of hardwoods for wood flooring. The functionalized wood surface also exhibited high wear resistance, which reached to the specification for commercial grade I impregnated paper laminated wood flooring. Additionally, the water resistance of the functionalized wood surface was significantly improved through lamination with Al2O3impregnated paper. The functionalized wood demonstrated high applicability for wood flooring.

High-entropy alloys (HEAs) provides a new way to develop new materials with adjustable performance due to their unique cocktail effect. Inspired by HEAs, a ceramic material with high-entropy effect has been developed, which was named high-entropy ceramics (HECs). With the introduction of the concept of entropy stability, research on HECs has developed rapidly. At present, research on the performance of HECs has extended to traditional performance such as thermomechanical performance, oxidation resistance, and magnetic properties, as well as emerging performance such as catalytic performance, optical properties, and radiation resistance. Based on the definition of HECs, this paper reviews the crystal structure and preparation methods of HECs and supplements the simulation calculation methods and descriptors which is suitable for HECs. In this paper, the performance of HECs at this stage is divided into traditional fields and emerging fields according to the application fields. A variety of performance regulation methods are reviewed, and the development and research directions of HECs are prospected.

Multi-principal component alloy has been proved to form disordered solid solution in most cases. However, multi-principal component alloy with single phase solid solution has a few disadvantages in mechanical properties, such as low strength or poor plasticity. Aiming at CoCrNi-based multi-principal component alloy with low strength, this paper proposed a method to enhance the multi-principal component alloy through composition design. CoCrNiVAlxmulti-principal component alloy was melted by non-consumable vacuum arc melting, and the content of σ phase in the multi-principal component alloy was changed by adjusting the content of Al element. With the addition of Al element, the fcc disordered phase in the multi-principal component alloy gradually went to the ordered L12phase with the same structure. When the amount of Al was 1.5 wt%, the compressive strength reached 2347 MPa and the hardness reached 760.8HV, which were 30% and 20% higher than the compressive strength (1828 MPa) and hardness (619.3HV) of CoCrNiV multi-principal component alloy, respectively. With the further increase of Al element to 2.0 wt%, the σ phase in the multi-principal component alloy increased further, resulting in the simultaneous decrease of strength and plasticity. The strengthening mechanism of multi-principal component alloy was analyzed, and the strengthening action of L12phase was confirmed. The results showed that the strengthening of multi-principal component alloy was mainly provided by L12phase strengthening (1229.55 MPa, 52.39%) and grain boundary strengthening (376 MPa, 16.02%). This paper provided a probable strategy to increase the strength of the multi-principal component alloy, which opened up a new idea for the composition design of multi-principal component alloy.

In this paper, the remelting process is applied to Laser Directed Energy Deposition (L-DED) to repair single crystal superalloys. The main formation modes of stray grains in single crystal epitaxial growth were analyzed, and the inhibitory effect of remelting process on stray grains in single crystal epitaxial growth using L-DED was studied. Comparative experiments between remelting and non-remelting processes have been conducted. Three process parameters in the remelting process: power, z-axis lift and cladding-remelting interval time were studied. The impact of different remelting process parameters on single crystal epitaxial growth and the formation of stray grains has been studied. Remelting has been shown to effectively prevent the formation of stray grains during the solidification of the melt pool, which are otherwise caused by the presence of unmelted powder during the powder feeding phase of the L-DED process. A cladding layer without stray grains on both sides is obtained. After remelting, the epitaxial growth structure can achieve larger cellular and columnar dendritic zones and smaller primary dendrite arms. A favorable epitaxial growth structure was obtained in this paper, under the optimized remelting process window.

Rotary friction welding (RFW) is a solid-state joining process that can be used to join different alloy systems such as aluminum-steel alloys. Rotary friction welding has become increasingly appealing for various industries due to the sustainable advantages that it offers, including overall cost reduction, weight minimization, and unique properties. However, the formation of brittle intermetallic compounds (IMCs) at the interface can be a challenge in the welding process of aluminum-steel alloys. This paper reviews the metallurgical characteristics of aluminum-steel alloy joints manufactured by rotary friction welding. The different types of intermetallic compounds that can form at the interface, as well as the factors that affect their formation, are discussed. The effects of rotary friction welding parameters on the microstructure and mechanical properties of the joints are also presented. Specifically, minimizing interfacial reaction layers via post-weld heat treatment and controlling the heat input during the process is crucial to suppressing the formation of intermetallic compounds. This study employed artificial intelligence modeling, specifically the artificial neural network - multilayer perceptron, to investigate the effect of various parameters on the ultimate properties of the parts welded together. Overall, this paper provides an excellent resource for industries looking to embrace rotary friction welding to tackle the challenge of dissimilar Al-steel joining.

High-energy particle irradiation-induced crystallization technology presents remarkable potential for precise nanostructure design. However, the fundamental mechanism behind this process remains a long-standing unsolved puzzle. In this paper, we used a high-energy electron beam as the irradiation source and amorphous Fe85B15alloy as a model system to investigate the behavior of irradiation-induced structural changes. Our experimental results show that the nucleation barrier in irradiation-induced crystallization ranges from 0.5 to 0.8 eV, depending on the temperature, much smaller than that observed in thermal-induced crystallization. Additionally, the nucleation entropy observed is −1.60 × 10−3 eV/K, and the entropic contribution to the nucleation barrier dominates over the enthalpic contribution. This paper provides compelling experimental evidence demonstrating that nucleation in irradiation-induced crystallization is not a thermally activated effect; instead, it is a process in which the amorphous state progresses through a series of intermediate short-range ordering configurations toward a crystalline state with the assistance of irradiation-induced atomic rearrangement.

In this paper, the microstructure and mechanical properties of CoCrFeNiMox(x = 0, 0.1, 0.3, 0.5, 0.7, and 1.0) high-entropy alloys (HEAs) prepared with high-vacuum arc melting method were studied in detail. After Mo-doping, the strengthening mechanism of HEAs mainly included the component segregation strengthening and the second phase strengthening. Cr and Mo elements were enriched at the grain boundary of HEAs, which leaded to the formation of σ phase and strengthens the alloys. The microhardness and strength increased with Mo contents, while the elongation decreased gradually. Among which, the higher microhardness, yield strength, and ultimate tensile strength of CoCrFeNiMo0.3alloy reach 205.96 HV, 292.22 MPa, and 593.25 MPa, respectively, in compared with other alloys. More importantly, the percentage elongation of which remains 37.36%, and the microhardness distribution was uniform with an average value of 7.4 GPa and an elastic modulus of 263.6 GPa. The research findings presented in this paper could serve as a valuable theoretical basis and practical foundations for the strengthening efforts of face centered cubic (FCC) HEAs.

Superalloys play a critical role in aerospace applications due to their exceptional mechanical properties at high temperatures. The application of magnetic fields to regulate superalloys presents novel avenues for optimizing microstructures, controlling solidification defects, and enhancing their high-temperature properties. This paper provides a comprehensive review of research findings on the influence of magnetic fields on the microstructure and properties of superalloys. It systematically elucidates the effects of different types and intensities of magnetic fields on alloy solidification. Moreover, this paper extensively explores the effects of various types of magnetic fields on the phase composition, microstructure, and properties of superalloys, including Ni-based and Co-based alloys, as well as high-entropy alloys. The underlying mechanisms behind the impact of magnetic fields on these alloy types are thoroughly analyzed. Finally, the last section offers a brief summary of the current development status and prospects of magnetic field-regulated superalloys.

In the dynamic landscape of advanced manufacturing, the confluence of laser powder bed fusion (LPBF) and machine learning (ML) has recently garnered significant attention in many applications. This review investigates the confluence of LPBF and ML, specifically within the specific domain of stainless steel. Firstly, it delves into LPBF principles, including an overview of critical process parameters and associated defects. Secondly, the paper meticulously addresses the distinct challenges posed by steel in additive manufacturing (AM), highlighting factors such as chemical composition, anisotropic microstructure, and oxide film formation, all of which require specialized considerations. Thirdly, the spotlight shifts to the pivotal role of ML, covering predictive modeling for process parameters, real-time defect detection, and quality control. This paper highlights recent advances, revealing how data-driven approaches can accelerate process understanding and part qualification. Eventually, this review offers insights into the future integration of ML in LPBF for steel, providing valuable perspectives on potential advancements in the field of AM.

Thermal barrier coatings (TBCs) play an important role in the thermal protection of alloy components in high temperature industries. Accurately characterizing and extracting mechanical properties of TBCs are crucial for structural design, performance optimization, failure prediction and lifespan assessment. Indentation test is an effective method for experimentally obtaining the mechanical properties and provides valuable insights into the elastic, plastic and fracture behaviors of TBCs at elevated temperatures. This paper aims to provide an overview of indentation mechanical evaluation of TBCs, including the mechanical properties at different temperatures, the mechanical property anisotropy, the microstructural and mechanical behavior under thermal exposure and/or thermal cycling, as well as the comparison of functional performance between conventional and nanostructured TBCs. Furthermore, this paper points out the main challenges and future directions from indentation investigations of TBCs. Finally, this paper is summarized and prospected.

This paper examines the influence of various factors, including the addition of nano-calcium carbonate particles (chemical processes, C) to CPBs, non-isothermal field curing temperatures (thermal factor, T), and field vertical curing stress (mechanical factor, M), on the self-desiccation capacity of CPB plugs. The assessment of self-desiccation involves the determination of pore water pressure (PWP) and volumetric water content (VWC) in the examined CPBs. Thermo-mechanical-chemical (TMC) column experiments were conducted to investigate the interaction among these factors and their collective impact on the evolution of PWP and VWC within the CPB plug. The findings underscore that each factor, both individually and in combination, significantly affects the magnitude and progression of self-desiccation in CPB plugs. Notably, the factors of elevated field temperature and the introduction of nano-calcium carbonate (NC) to the CPB exert the most substantial influence on the extent and enhancement of self-desiccation, whereas the impact of field curing stress in isolation is comparatively much weaker. The integration of nano-calcium carbonate, especially under non-isothermal conditions and concurrent field stress, emerges as a key contributor to enhanced PWP and VWC dissipation rates. The role of non-isothermal field curing temperature is underscored as a significant contributing factor in the self-desiccation of CPB plugs. The results presented in this paper will contribute to a more cost-effective design of CPB plugs and the improved optimization of CPB mixtures with nano-calcium carbonate particles.

Turtle shell dorsal armor comprises a typical lightweight laminated composite structural material, which is constructed by cuticle and bone layer, with high specific strength and high fracture toughness. The red-eared slider turtle, a widely studied species of turtle, has a rich hierarchical structure. In this paper, according to the structure of red-eared slider turtle shell dorsal armor and the characteristics of each layer as well as by taking into full consideration of the fine structure of cuticle and ventral cortex of the shell dorsal armor, two bionic foam silicone rubber sandwich structures of different levels were prepared. Low-velocity impact test and finite element simulation analysis were carried out to study the mechanical response, specific absorbed energy, and damage mode of the two bionic sandwich structures under different impact energies, hammerhead shapes, and hammerhead radii. By comparing the mechanical response and specific energy absorption with the existing ordinary sandwich structure, we find that the two sandwich structures modeled in this paper exhibit better impact resistance than the ordinary sandwich structure. The shape and radius of the hammer head have a significant effect on the energy absorption characteristics of the sandwich structure, and the damage mode under the hemispherical hammer head is mainly dominated by tensile tearing damage, while the damage mode of extrusion fracture is more obvious under the impact of the conical hammer head. With the increase of the radius of the hammer head, the absorbed energy and specific energy absorption of the sandwich structure increases.

Multi-wire arc additive manufacturing (MWAAM) enabled customized production with high deposition efficiency and low cost as compared to the common wire arc additive manufacturing (WAAM) technology. In this paper, two titanium alloy components were prepared using the MWAAM technique, and the microstructures, mechanical properties, and wear behaviors of Ti–6Al–4V (TC4) alloy and Ti-6.5A1-3.5Mo-1.5Zr-0.3Si (TC11) alloy were investigated. The results showed that the microstructure distribution of TC11 alloy prepared by MWAAM was more intensive and the length and width of the lamellar α-Ti phase were significantly reduced compared with that of TC4 alloy. The polar densities corresponding to the <110> texture in the two selected regions of the TC4 alloy and the TC11 alloy were 17.30 and 17.69, respectively. The proportion of the HAGBs of the TC4 sample and the TC11 sample were 99.07 % and 99.43 %, respectively. The average microhardness on the X–Y plane of TC4 and TC11 alloys were 316.17 HV and 366.14 HV, respectively, while the average microhardness on the Y-Z plane were 318.18 HV and 358.10 HV, respectively. The average compression yield strengths of TC4 and TC11 alloys were 836.61 MPa and 1088.33 MPa, respectively. The COFs of MWAAM TC4 and TC11 samples were stable at 0.479 and 0.455 under 20 N, respectively. The COFs of MWAAM TC4 and TC11 samples were stable at 0.472 and 0.432 under 60 N, respectively. The average yield strength, average ultimate strength, proportion of HAGBs, and microhardness of TC11 alloy were all higher than that of TC4 alloy. These results indicated that TC11 alloy had advantages over TC4 alloy in terms of mechanical properties and microstructure, with higher strength and deformation resistance. The properties of titanium alloy samples prepared by MWAAM were not lower than those of titanium alloy samples prepared by single wire WAAM, while MWAAM significantly better than single wire WAAM in deposition efficiency. The results obtained in this paper can help to prepare titanium alloy components with excellent mechanical properties more efficiently in MWAAM process.

In this paper, a novel coaxial continuous-pulsed dual-beam laser was proposed to join TC4 titanium alloy with QP980 high-strength steel, and magnesium alloy containing rare-earth elements (Mg-RE) was creatively as filler. The weld appearance, microstructure and mechanical properties of joints obtained by single-beam and dual-beam laser welding were compared and analyzed. And the evolution of bonding mechanism and the fracture mechanism with laser beam energy density was analyzed. The results showed that the appearance and mechanical strength of the joint obtained by dual-beam laser were better than that by single-beam laser. And the maximum tensile shear load of TC4/QP980 lap joint welded by dual-beam laser reached 303 N/mm, which was 124 % of that of single-beam laser welding. The bonding of Mg-RE with QP980 affected by temperature of laser welding and mainly depended on Gd and Y. They just diffused to QP980 under low power and reacted with Fe under high power. And the inter-diffusion of Zr of Mg-RE with Ti of TC4 produced to the bonding of Mg-RE with TC4. The roles of continuous laser and pulsed laser in dual-beam laser welding were revealed in this paper and it showed a great application potential of coaxial dual-beam laser welding technology in dissimilar metal joining.

Stereo Lithography Apparatus (SLA) has demonstrated improvements on surface-roughness and dimensional-accuracy of the precision casting prototypes in recent years, which however is still far from being satisfactory in industrial. One primary problem is the easy crack of the ceramic shell at sintering process originated from the high thermal expansion coefficient of the photosensitive resin. Herein, this paper aims to find a solution for the cracking problem of the SLA-prototyped ceramic shells. This paper introduces recent studies mainly focusing on the aspect of photosensitive resin modification, the hollow structure improvement inside the photosensitive resin prototype, the wax sheet pasting method on the weak part of ceramic shells, and the sintering process design of the photosensitive resin in ceramic shells. The performance of ceramic shells through these studies are evaluated, and a fundamental solution to the cracking problem of ceramic shells is thereafter prospected.

This paper reports on the successful synthesis of a novel alumina powder with a unique rose-like structure composed of alumina platelets, using the molten salt method. The synthesized powder was then utilized to prepare alumina ceramic with impressive mechanical properties. The influences of the synthesizing temperature of alumina powder on the microstructure and mechanical properties of alumina ceramic are investigated in details. The results indicate that the alumina ceramic prepared using the rose-like powder synthesized at 800 °C exhibits a high relative density of 99.5 %, flexural strength of 408.2 ± 18.7 MPa, and fracture toughness of 6.14 ± 0.63 MPa m1/2. The work presented in this paper will provide a useful guideline for the preparation of high-performance alumina ceramic materials in the future.

In the case of operating technical objects in conditions that accelerate material wear, it is necessary to adequately protect the object from the aggressive working environment. There are several possibilities, ranging from applying surface coatings (paint, varnish, galvanic layers) to the use of composites. An example of such a material is a composite formed by explosively welded AA2519, AA1050, and Ti6Al4V alloys. Since the described material is relatively new, its mechanical properties are still being determined. Therefore, in this article, the results of research and their analysis regarding the fracture toughness of the described composite in comparison to the fracture toughness of the base materials in the selected range are presented. The main objective of study was to determine the crack tip opening displacement (CTOD) values for the AA2519-AA1050-Ti6Al4V laminated material explosively welded under ambient and cryogenic conditions. The tests were carried out to determine the effect of the aforementioned temperature conditions on selected properties of the tested laminated material. This paper presents the theoretical basis and the adopted testing methodology. The experimental results obtained and their analysis are also presented. Thanks to the analysis, the effect of cryogenic conditions on the value of the crack tip opening displacement was observed. Moreover, the state of knowledge presented in earlier publications on crack tip opening displacement determination for base materials, i.e. AA2519 and Ti6Al4V, has been extended. The paper also presents a CTOD determination procedure for laminated material based on the knowledge on the mechanical properties of the base materials.

The wear resistance of the part surface has become an important factor affecting its own service life. Laser cladding (LC), as a surface modification technology, can prepare a coating with good metallurgical bonding with the substrate, which can significantly improve the wear resistance of the material surface. High entropy alloys (HEAs) are an emerging coating material with excellent wear resistance. Therefore, this paper reviews the latest development status in wear resistance of laser cladding-high-entropy alloy coatings (LC-HEACs) in terms of the HEAs material system, LC process parameters, strengthening phase, amorphous phase strengthening, assisted cladding, and post-treatment. At the same time, this paper also expounds on the mechanism of LC-HEACs enhancing the surface wear resistance of materials, and the current research status of LC-HEACs in different engineering materials and application environments. Finally, the current research deficiencies, challenges, and future development trends of LC-HEACs in the field of wear resistance are also elaborated, and it is expected to provide some references for their future development and applications.

M23C6carbide can precipitate simultaneously on both sides of austenite grain boundary in Fe–15Mn–3Al-0.7C steel tempered at 600 °C. In this paper, the morphology and growth behavior of M23C6are studied by means of OM, SEM and TEM. The results show that the morphology of M23C6located on both sides of grain boundary is different. On one side of the grain boundary, the carbides appear to be dispersed and disconnected, each with an irregular particle-like morphology, while on the opposite side, they are dispersed along the grain boundary in a short-rod morphology, and the adjacent ones tend to join together to form a network structure. In fact, regardless of which side of the grain boundary the carbides are on, they exhibit a definite growth behavior, growing along the close-packed plane and grain boundary. Also, the morphology of M23C6depends on the angle between the close-packed plane and the grain boundary. In addition, twin structures with the same orientation can be found in both austenite and M23C6. A notable distinction between them is that there is a flat twin plane in the austenite twin structure but not in the carbide twin structure. Therefore, this paper highlights that the formation of these two twin structures is different. The austenite twin structure is caused by quenching treatment, while the carbide twin structure is formed by a new method called “growing-contacting”.

To reveal the microstructure forming mechanism of laser/ultra-high frequency (UHF) induction deposition, this paper developed a microscopic phase-field (PF) model to numerically investigate dendrite growth during solidification. The macroscopic model of molten pool evolution is adopted to provide the solidification conditions for the microscopic PF model. The dendrite growth during laser deposition is simulated to evaluate the effect of UHF induction heat on the dendrite growth. Results show that because of the high temperature gradient and cooling rate, the PDAS of laser-UHF induction hybrid deposited layer is less than that of the laser deposited layer. The UHF induction heat also leads to a high flow velocity of the molten metal during laser-UHF induction hybrid deposition. The high flow velocity contributes to the decrease in PDAS by inhibiting the interdendritic enrichment of solute. During laser-UHF induction hybrid deposition, a higher solute gradient is present in the tip region of dendrite arm, leading to a faster dendrite growth rate. The UHF induction heat also increases the solute distribution coefficient during deposition, which further inhibits the element segregation. Under the action of UHF induction heat, a low interdendritic solute gradient and an evenly distributed solute can be obtained, thus helping increase interdendritic undercooling degrees and decreasing the PDAS. The simulated PDAS and solute distribution have good consistency with the experimental results. The spectral analysis of EDS line detection indicates that the laser-UHF induction hybrid deposited layer has a more refined microstructure and weaker element segregation than the laser deposited layer does.

Nuclear energy is essential for the future development of countries. However, both structural and functional components of nuclear power equipment are facing severe challenges of nuclear irradiation damage after experiencing irradiation growth and irradiation creep. How to avoid irradiation damage to nuclear power equipment has become a hotspot in international research and development of surface protection technology. Deposition of protective coatings on the underlying object surface or in bulk materials has been considered as a near-term solution to enhanc functional components. Different substrate materials are selected according to other service conditions within the reactor. Suitable material selection combined with relevant optimization can significantly increase the service life of materials. This review summarizes recent research on several categories of anti-irradiation coatings prepared by physical vapor deposition technology for current industrial applications. These includes metallic, ceramic, composite and high entropy alloy coatings. The review endeavors to impart a thorough understanding of the properties of these selected anti-irradiation coatings, from the fundamental aspects of their substrate materials to their practical applications across diverse settings. It explores not only the current research progress but also the potential avenues for future advancements. Additionally, the intricate relationships between coating formulations, their resistance to irradiation, and their ultimate performance in various environments are illuminated in this paper.

Environmental and economic factors have driven research into the recycling and applications of recycled carbon fibres (rCF). This paper presents a comparative study characterizing and comparing the mechanical and thermal performance of recycled short milled carbon fibre (rSMCF) on virgin and recycled polypropylene composites. The effects of rSMCF on VPP and RPP on mechanical performance were analysed and compared. At 5 wt% rSMCF, recycled polypropylene achieved 52.3% and 47.3% improvement on tensile and flexural modulus, while at the same rSMCF loading, virgin polypropylene only improved 37.7% and 17.5%, respectively. The un-notched impact strength of RPP-based composites reduced from 83.2 kJ/m2to 60.1 kJ/m2when rSMCF content increased from 1 wt% to 5 wt%, indicating future work should enhance the fibre/polymer interface performance. Crystal contents (χ0) of the PP/rSMCF composites were investigated by differential scanning calorimetry (DSC), and the results were analysed and mapped to the mechanical performance. The results of this study propose a novel scalable method for the production of high-performance VPP/RPP composite materials using rSMCF.

The dissimilar welding between aluminum alloys and ultra-high strength steels (UHSS) can realize the structural lightweighting in the manufacturing of vehicle bodies. However, brittle Al–Fe intermetallic compounds (IMCs) are easily formed during welding, limit the industrial application of Al/steel hybrid structure. In this paper, solid rivet resistance riveting welding (RRW) is adopted to join AA6061-T6 aluminum alloy to CR1180T UHSS. This method employs a solid steel rivet to pierce the aluminum alloy workpiece under a piercing current, then a welding current is conducted to weld the rivet to the steel sheet. The influence of rivet leg height, rivet diameter, taper of rivet leg and volume ratio of rivet cap to rivet leg on the joint performance of RRW Al/steel are investigated. The results show that a rivet with small dimension will make it difficult to form effective piercing and welding, and a rivet with too large dimension will increase the difficulty of piercing and welding. With suitable design of rivet dimensions and selection of piercing and welding parameters, the maximum average tensile-shear force of RRW joint reaches 10.8 kN.

In order to solve the problem of poor performance of welded joints of steel and aluminum dissimilar materials, this study proposes the use of ceramic particle-reinforced aluminum alloy as an alternative to traditional aluminum alloy for welding, effectively overcoming this problem. In this paper, the laser welding of stainless steel/6061 aluminum alloy (SA) and stainless steel/TiC–TiB2duplex nanoparticle-reinforced 6061 aluminum alloy (SRA) was realized. The effect of ceramic nanoparticles on the microstructure and mechanical properties of SRA joint was systematically studied, and the strengthening mechanism of nanoparticles was revealed. Under the same process parameters, the melting zone of SRA joint is larger and the intermetallic compound (IMCs) layer is narrower. Moreover, the grain size of the brittle Fe–Al compound phase in the IMCs layer is significantly reduced, which effectively inhibits the initiation of cracks at the steel/aluminum interface. The study shows that ceramic particles have a pinning effect on the dislocations, limiting the grain growth, reducing the thickness of the intermetallic compound layer, and decreasing the content of the brittle FeAl3phase. Moreover, ceramic nanoparticles promote the formation of Mg2Si strengthened phase at the grain boundary, further hinder the dislocation movement and improve the strength of the joint. Under the welding power of 3400 W and welding speed of 31 mm/s, SRA joint achieves the maximum tensile shear of 1718 N, which is 15% higher than the strength of SA joint.

For the development of new energy automobile industry and the trend of automobile lightweight have put forward a huge demand for high-strength lightweight materials, so developing high strength aluminum alloys is particularly momentous. As the most widely used aluminum alloy, 6000 series aluminum alloys (Al–Mg–Si alloys) have the advantages such as better mechanical properties, outstanding welding properties, excellent formability and fine processing capability, and therefore have obtained great attention as the structural materials. In addition, the Al–Mg–Si alloys with low density and corrosion resistance not only reduce the total weight of the car, but also extend the service life when subjected to chemical corrosion, which effectively achieve energy saving and emission reduction. This paper summarizes the research progress of 6000 series aluminum alloys, in particular, and reviews the methods of microalloying and particle strengthening, and their effects on the microstructure and properties of the alloy, thus providing a reference for the subsequent development of high-performance aluminum alloys in automobile and aerospace industries.

Controlling continuous cooling is an important means to control the most important mechanical properties of bainitic steel for frogs in railroad applications. In this paper, a bainitic steel for railway frogs is taken as the research object. By designing different cooling rates in the bainitic transformation medium temperature region, the effect of cooling rate on fatigue crack propagation rate was studied. The results show the sample of 4 °C/s cooling rate exhibits higher strength and impact toughness, while the crack propagation rate near the threshold is significantly lower and the threshold is relatively higher at 0.1 °C/s cooling rate. This is related to the fact that more massive blocky retained austenite and coarse microstructure in the sample at 0.1 °C/s cooling rate are more favorable to the occurrence of crack closure effect, especially in the near-threshold region. The fatigue crack propagation rate of the tested steel in the stable propagation region at 4 °C/s cooling rate is slightly higher than that at 0.1 °C/s. This is related to its complex interface distribution characteristics. However, with the increase of Δ K, the tested steel at 0.1 °C/s cooling rate tends to preferentially fail, which is related to its poor toughness.

This paper is one of the first studies focusing on phase and microstructure formation mechanisms during reactive sintering of AlxCoCrFeNi (x = 0.3, 1) high entropy alloys (HEAs). The alloys have been prepared by mechanical activation followed by spark plasma sintering (SPS). Both powders are subjected to gluing to the milling vials and the phenomenon intensifies with Al content, resulting in a more important mechanical alloying delay for the equiatomic composition. The temperature influence on phase and microstructure formation was investigated by SPS from 550 to 1100 °C. Al0.3CoCrFeNi reactive sintering led to a face-centered cubic (FCC) solid solution with a grain size around hundreds of nanometers with nanometric intergranular B2 precipitates which content and size reduced with the temperature increase. Grain growth was observed at prior particle boundaries due to dynamic recrystallization, a phenomenon that can be controlled through modification of the milling and sintering steps, leading thus to tailored grain sizes. For the AlCoCrFeNi composition, temperature increase favors secondary FCC formation and leads to sigma phase precipitation. A dual homogeneous-heterogeneous microstructure is obtained due to the important gluing leading to insufficient milling. The dynamic recrystallization at prior particle boundaries promotes also body-centered cubic (BCC) to FCC phase transition. Therefore, the proposed reactive sintering route allows to obtain, for the equiatomic composition, alloys exhibiting very fine microstructures, with higher FCC fraction content than by conventional metallurgy processes.

The prolonged mechanical performance degradation and failure of elastic components in mechanical systems can pose significant safety risks and disrupt related operations. While helical compression springs' mechanical behavior and failure mechanisms at high temperatures have been well-studied, their mechanical properties and microstructural deformation mechanisms at extreme cryogenic temperatures remain largely unexplored. This paper conducts experiments to investigate the detailed mechanical properties and microstructural evolution of Ti-6Al-4V helix springs under such conditions. Initially, we examined the mechanical properties at cryogenic temperatures and compared them with those at high temperatures. It was observed that the logarithmic constitutive model applicable at high temperatures does not suitably describe the spring's mechanical behavior at cryogenic temperatures. At extremely low temperatures, the mechanical properties of the spring were enhanced. Furthermore, we characterized the microstructural deformation mechanisms using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM), including twinning, slip activation, and dislocation evolution. The findings suggest that the deformation mechanism in Ti-6Al-4V springs under cryogenic conditions is predominantly governed by twinning and basal and prismatic slip. Due to the significant increase in the critical resolved shear stress (CRSS) of the pyramidal slip systems at cryogenic temperatures, these slip systems may not be activated during the deformation process. Additionally, the volume fraction of twinning shows a significant positive correlation with both cryogenic temperature and mechanical stress.

A study on how corrosion and mechanical characteristics of friction stir welded joints are affected by processing parameters employed during the welding and the post-weld heat treatment administered on the welded materials has been reported in this paper. This study specifically investigated the effects of variable parameters such as the tool rotational and welding speeds and the post-weld heat treatment on the mechanical and corrosion behaviour of the friction stir welded dissimilar 6101-T6 and 7075-T651 Aluminium Alloys. The welded samples were characterized by the evolving microstructure and mechanical characteristics. The results show that the tensile strength of the joints decreases from 154 MPa to 144 MPa when the rotational speed increases from 950 rpm to 1550 rpm. However, the tensile strength increases from 138 MPa to 154 MPa with an increase in the welding speed from 20 mm/min to 110 mm/min. This is due to high heat input at higher rotational speed which weakens the bonding strength at the joints. The corrosion behaviour was observed to differ at different parameters. The corrosion inhibition efficiency was highest at a rotational speed of 950 rpm, welding speed of 65 mm/min, and lowest at 950 rpm and 20 mm/min. It was observed that the Post-Weld Heat Treatment (PWHT) process enhanced the mechanical properties as a result of an improvement in the grain refinement but lowered the corrosion resistance. This study is significant as it informs the basis for the optimization of processing parameters and post weld heat treatment for dissimilar aluminium alloys for the grades considered in this study.

In this paper, novel application possibilities of CuO nanoparticles were investigated in SAC0307 solder alloy for composite soldering purposes. CuO nanoparticles in 0.25 and 0.5 wt% were mixed into the solder paste to produce composite solder joints. Solder joints were manufactured using standard surface mounting technology from different solder pastes. The solder joints were loaded in an 85 °C/85RH% temperature and humidity test for 4000 h. It was found that the CuO composite solder joints showed improved mechanical quality due to the microstructural refinement, which was studied using scanning electron microscopy (SEM) and focused ion beam (FIB) analysis. On the other hand, the corrosion resistance of CuO joints decreased, as they suffered localized corrosion extensively, which produced longer and more Sn whiskers on their surface than on the reference SAC0307. Density functional theory (DFT) calculations proved that CuO can bond to Sn, but CuO is not chemically inert in the solder bulk. CuO can start a cyclic reaction with the dispersed Cu6Sn5intermetallics, which produces SnO2in the solder bulk, ultimately enhancing corrosion. Therefore, CuO nanoparticles are suggested to be applied only in non-corrosive environments, such as space applications.

TiO2–Y2O3–ZrO2composite ceramics exhibit excellent abrasion resistance, corrosion resistance, and high-temperature resistance, making them vital structural-functional materials in ceramics and refractories. The key to preparing high-quality TiO2–Y2O3–ZrO2ceramic powders lies in controlling the agglomeration rate, which can be optimized by choosing an appropriate drying method. This study utilized microwave drying techniques to dehydrate TiO2–Y2O3–ZrO2ceramic powders. It was found that the average drying rate is proportional to initial masses, initial moisture contents and microwave heating powers. To describe the drying process, four models—the Quadratic, Wang and Singh, Modified Page, and Page—were employed. The best model for the drying process was the Modified Page model. The specimens were analyzed to assess the alterations in the samples pre and post-drying by scanning electron microscopy and Fourier transform infrared spectroscopy. The findings revealed that microwaves can hasten the drying process of TiO2–Y2O3–ZrO2and enhance its spread. Utilizing Fick's second law, the effective diffusion coefficient was ascertained, showing an inverse proportionality to the sample mass, and a proportionality to the microwave heating power and initial moisture content. Using the Arrhenius exponential model, it was ascertained that the microwave drying process's activation energy stands at 13.81834 W/g. This paper demonstrates that microwave drying effectively achieves efficient drying and lays the theoretical and experimental groundwork for the microwave heating and drying of other powdered materials.

Nickel-base alloy is a type of metal material with excellent properties and is widely used in many fields. However, in the harsh environment of the acid solution, corrosion causes the reduction of the service life of the alloys, thereby limiting the alloys' use and development. In this paper, the effect of Chromium (Cr) content on the microstructure and corrosion behavior of nickel-based alloys in hydrochloric acid (HCl) was studied by scanning electron microscopy (SEM), energy dispersive spectrum (EDS), electron backscatter diffraction (EBSD) and electrochemical workstation. Meanwhile, X-ray photoelectron spectroscopy (XPS) was used to investigate the composition and properties of the surface passive films. For the Cr20 and Cr30 alloys with a single face-centered cubic (FCC) structure, the Cr2O3content in the passive films increased with the Cr content, effectively improving the corrosion resistance. As the Cr content continued to increase, the second phases having a body-centered cubic (BCC) lattice were precipitated both in the Cr40 and Cr50 samples, inducing microgalvanic corrosion, thus deteriorating the corrosion resistance. XPS results showed that, in the Cr30 alloy, the relative content of Cr2O3and the bound water were the highest, indicating that its passive film had the best corrosion resistance. For the passive film, the pitting resistance was related to Cr content, appropriate Cr content improved the corrosion resistance.

In order to increase the productivity, new generation of selective laser melting (SLM) machines are evolving towards higher power lasers. In this paper, the microstructure evolution and mechanical properties of 24CrNiMoY alloy steel fabricated by high power selective laser melting (HP-SLM) have been reported. The results show that with the optimized laser power over 400 W, the powder layer thickness can be increased to 60 μm, and the theoretical productivity reaches 7.2 mm3/s, which is more than two times of the normal SLM technology. As the laser energy density increases, the structure of melt pool changes from a thermal conduction mode to a keyhole mode, and the microstructure mainly consists of martensite, bainite and pre-eutectic ferrite, and the phase composition of the specimen is α-Fe phase and a small amount of Fe3C,with fine grain size and irregular orientation. When the laser energy density is 68 J/mm3, the microhardness of the specimen is 410HV0.2, the tensile strength reaches 1121 MPa and the percentage elongation after fracture is 11.5%, which realizes a good match between strength and ductility. The fine tempered martensite and lower bainite in the microstructure is the key to excellent strength and ductility. This research is of guiding significance and serves as a technical reference for understanding the microstructure evolution and mechanical properties of HP-SLM 24CrNiMoY alloy steel.

Magnesium alloys have received a lot of attention in aerospace, automotive, electronic communications and other fields due to their low density, high specific strength and damping performance. However, magnesium alloy sheets prepared by conventional thermomechanical processing usually have a strong basal texture, resulting in poor formability. In this paper, Mg–Mn–Ce alloys with good plastic forming ability were prepared by studying and optimizing the annealing process. Under the low-temperature annealing condition, it can promote the static recrystallization and grain refinement of Mg–Mn–Ce alloy, and also eliminate the internal stress. With the increase of annealing temperature, a large amount of dispersed Mg12Ce as a stable second phase effectively hindered the grain boundary migration, while the nanoscale α-Mn forms a fine second phase to inhibit grain growth, and both of them together greatly stabilize the deformation structure of the alloy, and maintain a good grain organization under the condition of annealing temperature of 300 °C and holding time of 30 min. The present work also improves the Arrhenius constitutive equation for the Mg–Mn–Ce alloy with respect to the degree of deviation, which significantly improves the accuracy of the model in predicting the thermoforming behavior. Meanwhile, to address the shortcomings of the traditional forming method of magnesium alloy, the processing process of spreading the centrifugal casting tube flat is proposed, the forming process is simulated, and the location of easy breakage in the forming process is predicted. These findings provide microanalytical support for the improvement of forming properties of magnesium alloys by annealing.

In this paper, isothermal thermal compression tests were carried out on Al–Zn–Mg–Cu alloys at varying deformation temperatures (360°C∼440°C) and strain rates (0.001s−1∼10s−1) using a Gleeble-3500C thermal simulation tester. Based on the true strain stress data obtained from the tests, the flow behavior of Al–Zn–Mg–Cu alloys during thermal deformation was investigated. Through a comprehensive consideration of deformation temperature, strain rate, and strain compensation, a high-precision constitutive model was established. Additionally, the specimens subjected to hot compression were further treated with solution annealing for different durations (0 h–2 h) to investigate the static recrystallization (SRX) behavior and the associated microstructural evolution of the alloy during the solution treatment process. Electron Backscatter Diffraction (EBSD) was employed to characterize the microstructure evolution of Al–Zn–Mg–Cu alloy under various deformation and solution treatment conditions. The EBSD data were further processed and analyzed using the MTEX toolbox. The results revealed that dynamic recovery (DRV) is the predominant softening mechanism during the deformation process, accompanied by a small amount of dynamic recrystallization (DRX). The dynamically recrystallized grains exhibit a random crystallographic orientation. Further investigation showed that low temperature and high strain rate conditions are unfavorable for the occurrence of dynamic recovery and dynamic recrystallization during the thermomechanical processing. However, dislocations accumulated during deformation provided sufficient stored energy for the growth of static recrystallized grains during subsequent solution treatment, with static recrystallized grains predominantly forming at grain boundaries.

Finding suitable co-catalysts to help metal sulfides achieve effective bulk phase and surface charge separation is the key to improving their photocatalytic performance. In this paper, two-phase 1T-2H MoSe2was loaded onto the surface of Mn0.4Cd0.6S solid solution with a twin crystal structure, and the 1T-2H MoSe2/Mn0.4Cd0.6S Z-type heterojunction structure was successfully constructed to realize the high efficiency of hydrogen production in the visible light. The metallic properties of the 1T phase can significantly improve the catalytic activity of MoSe2. The transition from the 2H to the 1T phase can lead to the creation of extra defects, such as unsaturated Mo and Se, thereby increasing the number of active sites on the photocatalyst surface. The two crystalline phases are staggered and form homogeneous junctions within them in the twin crystalline structure Mn0.4Cd0.6S prepared under an alkaline environment, which gives it excellent bulk and charge separation properties. After loading, the 1T phase MoSe2at the interface of MoSe2and Mn0.4Cd0.6S can accelerate the charge separation between the interfaces, and the Z-type heterojunctions formed by the two and the better retention of useful excitation electrons and holes. The 1% 1T-2H MoSe2/Mn0.4Cd0.6S could achieve a notable hydrogen production rate of 12.34 mmol ∙g−1∙h−1, surpassing that of the Mn0.4Cd0.6S solid solution. This non-precious metal-loaded homojunction photocatalyst effectively harnesses solar energy to produce clean H2under mild conditions, giving a promising prospect for practical applications and laying the groundwork for further exploration of MnxCd1-xS photocatalysts.

In response to the shortcomings of traditional Gas Tungsten Arc Welding (GTAW), such as low penetration, slow welding speed, and low production efficiency, an Ultra-High-Frequency Adjustable Multi-Pulse Gas Tungsten Arc Welding (UFMP-GTAW) process is proposed. This process more effectively concentrates the temperature distribution of the welding arc. To characterize the arc morphology and its dynamic changes, high-speed photography captured ten images of the UFMP-GTAW welding arc within one cycle. The arc image processing algorithm proposed in the paper was used to study the arc's variation characteristics over one cycle. This algorithm includes binarization, arc segmentation, and edge detection to obtain arc morphology parameters. The arc symmetry algorithm is used to symmetrize the arc images for Abel inversion, resulting in the emission coefficient distribution. Further calculations provide the temperature distribution, electrical conductivity distribution, and current density distribution of the arc. Analysis reveals that changes in arc temperature, electrical conductivity, and current density lag behind changes in current. The temperature of the arc spreads from the central axis to the surrounding arc space. When high-frequency current variations occur, the heat input generated by the current increase takes time to transfer to the entire arc space. Conversely, if the current suddenly decreases, the heat input rapidly diminishes. However, because heat transfer takes time, the arc space remains relatively stable for a short period, making the ultra-high-frequency arc form more stable.

Laser powder bed fusion (LPBF) Al–Li alloy technology demonstrates adaptability to the development requirements of structural complexity and functional integration, making it a promising area of research in additive manufacturing for the aerospace, defense industry, and other fields. However, challenges such as microstructure anisotropy and metallurgical defects inevitably arise during the LPBF process of lightweight alloys, significantly impeding further enhancements in their formability properties. Some improvement measures offer a viable solution to enhance the microstructure, mitigate metallurgical defects, and optimize residual stress distribution in additive structures, thereby enabling high–performance Al–Li alloy production by LPBF. This paper first introduces the fundamental principle of LPBF and discusses the process of parameter optimization for LPBF Al–Li alloys. It then describes the typical microstructures and common metallurgical defects of LPBF Al–Li alloys, along with examining the evolution process of microstructures and formation mechanism of metallurgical defects. Specifically, it focuses on discussing the influence of Li element on solidification structure. On this basis, it presents the mechanical properties and anisotropy of mechanical properties for LPBF Al–Li alloys. Afterward, a comprehensive review is provided of the current research status regarding LPBF improvement measures, including powder alloying, heat treatment, and other technologies. Emphasis is placed on improvements in microstructure anisotropy and reductions in metallurgical defects through these improvement measures. Finally, this article summarizes the research progress made in LPBF Al–Li alloys and its improvement measures while also prospecting future research work.

In this paper, Ti6Al4V alloy and Ti6Al4V-SiCw composites were formed by selective laser melting (SLM) and electrochemical corrosion experiments were carried out. The effects of different SiCw contents and solid solution aging heat treatment on the corrosion properties of the composites were systematically studied, and the corrosion mechanism of Ti6Al4V-SiCw composites was revealed. The results show that Ti6Al4V-1SiCw composites have better corrosion resistance than Ti6Al4V alloy. After solution and aging heat treatment at 1050 °C, Ti6Al4V-1SiCw composites have better corrosion resistance. The main reasons for the improvement of the corrosion performance of the composites are as follows: (i) The high-density grain boundaries formed by grain refinement of the composites have higher energy and are more likely to react to form a stable passivation film. (ii) The microstructure of Ti6Al4V-SiCw composites is equiaxed α phase, which is easier to form stable passivation film than metastable α′-Ti phase. (iii) The presence of ceramic particles makes more microcells formed in the titanium matrix, which promotes the formation of soluble [TiCl6]2-complexes. The formation of passivation film on the surface of Ti6Al4V-SiCw composites was accelerated.

Recent explosions have prompted researchers to investigate the vulnerability of civil structures, leading to an increased demand for blast-resistant buildings. Laminated glass (LG) panels in glazed facades boost resilience, yet understanding glass fragment interaction with interlayers remains incomplete. This paper presents an integrated experimental-computational study on strain localization in LG polymeric interlayers to accurately simulate their response, addressing this gap. Uniaxial tensile tests were performed on the polymeric interlayer materials polyvinyl butyral (PVB) and SentryGlas® (SG), commonly used in the design of LG in blast-resistant glazing systems. Digital image correlation was used to characterize strain localization within the material. The experimental results were used to calibrate material model parameters to be used in the modeling of LG systems. A three-network viscoplastic (TNV) material model for SG interlayer was calibrated using PolymerFEM software. Yeoh hyperelastic material model parameters were calibrated for the quasistatic response of PVB. A finite element computational model was developed using Ansys LS-DYNA software and validated with experimental data. The study results showcase finite element modeling's ability to accurately predict both the hyperelastic response of PVB and the post-peak large strain behavior of SG interlayer materials by 8% and 3.6%, respectively.