To prepare Cu/Al laminated composites with a lightweight structure and excellent thermal and electrical conductivity, vacuum hot-press diffusion bonding was employed to investigate the effects of the bonding process on interfacial microstructure evolution, microhardness, and thermal/electrical properties. The results show that the diffusion layer from Al to Cu is sequentially composed of Al(Cu) solid solution, Al2Cu, AlCu, Al2Cu3, Al4Cu9, and Cu(Al) solid solution. As temperature increases and time extends, overall performance tends to decline. The optimal metallurgical bonding is achieved at 550 degrees C for 4 h, with an electrical conductivity of 52.69% IACS and a thermal conductivity of 268.3 W/(m & sdot;K). Under the optimal process, increasing the Cu/Al layer thickness from 0.5/0.5 mm to 3/3 mm significantly improves the electrical and thermal conductivities, reaching 73% IACS and 316.14 W/(m & sdot;K), respectively. Based on the growth kinetics and interfacial diffusion mechanism of intermetallic compounds (IMCs), the results reveal that IMCs initially nucleate as island-like structures and gradually transform into continuous multi-layered diffusion layers. Heat transfer mechanism analysis indicates that the thermal conductivity of the composite is mainly controlled by the bulk thermal resistance of IMCs, interfacial thermal resistance, and the gradient solid solution region in the Cu matrix.

In this study, WC-10Co-4Cr composite coatings with various TiC contents (0, 5, and 10 wt.

As a lightweight and high-strength composite material, syntactic foam has extensive applications in marine engineering and aerospace fields. During their service life, cyclic loads often lead to the degradation of material properties, which in turn affects the safety of structures. Therefore, in this paper, uniaxial cyclic loading experiments at 70 % stress level were conducted on hollow glass microspheres (HGMs) /epoxy resin syntactic foams, and the degradation law of mechanical properties of foam materials under fatigue loads was systematically studied. In addition, the microscopic fatigue damage mechanism was discussed in combination with SEM and X-ray microCT technology. Research shows that under cyclic compressive loading, the residual strength of syntactic foam initially decreases slowly. At this stage, the internal damage of the material mainly consists of interface debonding, microcracks in HGMs, and microcracks in the interfacial layer resin. Subsequently, the residual strength will briefly increase. The occurrence of this stage is mainly related to the optimization of the internal stress field of the material and the transfer of the load-bearing body. In addition to the expansion of existing damage, the material will also generate interface/matrix extension microcracks, matrix microcracks, and the fracture of HGMs. Finally, the residual strength continuously and rapidly decreases. After 60 cycles of loading, the residual strength ratio is 88.4 %. At this point, the microcrack network connects and merges to form through cracks, the microstructure fails, and the macroscopic mechanical properties continuously decline.

Ti/Al3Ti laminated composites reinforced by graphene nanoplatelets (GNPs) were fabricated by vacuum hot-pressing sintering. The influence of GNPs on microstructure, interface structure, and mechanical properties of the composites was studied. The results showed that the mechanical properties of the composites were closely related to the distribution state of GNPs and the interface bonding of GNPs/Al3Ti. In 0.1 wt.% GNPs composites, GNPs was uniformly distributed and exhibited an intact and straight morphology. GNPs formed a good bonding interface with Al3Ti through van der Waals forces and atomic diffusion bonding. In 0.3 wt.% GNPs composites, GNPs agglomerated in the Al3Ti centerline and exhibited a wrinkled morphology, which destroys the structural integrity of the Al3Ti layer. The formation of interface brittle TiC and interface defects weaken the interface bonding of GNPs/Al3Ti. Mechanical property tests revealed that the tensile strength and failure strain of the composites first increased and then decreased with the increase of the mass frcation GNPs, while the compressive properties continued to improve. The tensile strength and failure strain of the composites with 0.1 wt.% GNPs were 711 MPa and 5.42%, respectively, representing an increase of 14% and 183% compared to the unreinforced composites. The compressive strength and failure strain of the composites with 0.3 wt.% GNPs were 1562 MPa and 6.36%, respectively, but the tensile properties severely deteriorated. The severe decrease in interface shear strength caused by the agglomeration of GNPs at the Al3Ti centerline and differences stress response mechanism are the fundamental reason that why the composites exhibit high compressive strength but low tensile strength. Therefore, inhibiting the agglomeration and improving the interface bonding of GNPs/Al3Ti are the key to achieving synergistic strengthening and toughening of GNPs-Ti/Al3Ti laminated composites.

Layered structural parameter are important factors affecting the mechanical properties of laminated composites. In this paper, Ti/Al3Ti laminated composites with two layered structural parameters of equal layer thickness and layer thickness ratio were prepared by vacuum hot-pressing technique. The microstructure and grain characteristics of the composites were systematically investigated. The effects of layered structural parameters on the mechanical properties were analyzed through tensile testing and DIC. Results revealed that the microstructure exhibited a "fine-coarse-fine" grain distribution gradient from the Ti/Al3Ti interface to the centerline, accompanied by high GNDs. As the layer thickness and layer thickness ratio increased, the number of internal cracks and voids increased, and the average grain size increased, while the GNDs decreased. The strength and toughness of the composites initially increased and then decreased with the increase of layer thickness and layer thickness ratio. When the original thickness of Ti layer was 500 mu m and the original thickness of Al layer was 200 mu m, the composites achieved a tensile strength of 625 MPa and a failure strain of 1.91 %. The fracture micromorphology revealed that the Ti layer was ductile fracture, and the Al3Ti layer was a mixed model of transgranular and intergranular. Inhibiting strain localization through structural parameter optimization is the key to achieving the synergistic enhancement of strength and toughness. This study reveals the relationship between layered structure parameter and microstructure characteristics, local strain evolution, and macroscopic mechanical properties in laminated composites, providing ideas for optimizing their mechanical properties.

To overcome the limitations of traditional single-variable experiments, this study employs response surface methodology (RSM) with Box-Behnken design (BBD) to optimize key vacuum hot-pressing process parameters (plate thickness, holding time) for Mg/Al laminated composites, establishing quantitative relationships between parameters and mechanical properties. At Mg plate thickness of 0.5 mm, Al plate thickness of 0.1 mm, and 6h holding time, the composites show excellent specific bending strength (162 N m/kg) and specific compressive strength (183 N m/kg). Furthermore, combined with the Optimal (custom) design, the influence of structure composition on mechanical properties is revealed. The results show that the residual Mg layer has a positive regulation effect on the mechanical properties. Although the increase of the residual Al layer reduces the strength, it improves the plasticity. The regulation of intermetallic compounds on mechanical properties shows outstanding nonlinear characteristics. Fracture mechanism analysis reveals that cracks preferentially initiate in brittle intermetallic compounds during three-point bending, subsequently propagating along a ductile-brittle alternating path. The difference in the structural composition of the composites causes different combinations of fracture modes, mainly involving brittle phase fracture, interfacial delamination, ductile layer shear tearing and brittle phase induced interfacial debonding. Under compressive loading, the composites also exhibit mixed mode fracture, specifically manifesting as brittle fracture of intermetallic compounds, shear fracture of the Mg layer, and plastic instability failure of the Al layer. The process-structure-property correlation established and fracture mechanism revealed in this study hold significant implications for optimizing vacuum hot-pressing processes and designing high-performance Mg/Al laminated composites.

Zr-based amorphous alloys possess excellent glass-forming ability and high energy densi-ty,which facilitate the development of new energetic fragments.However,their poor plasticity limits their application in fragment-based systems.This study aims to investigate the Zr-Al-Ni-Cu alloy system by substituting Hf for Cu to examine its effects on the glass-forming ability and mechanical properties of Zr55Al10Ni5Cu30-xHfx(x=0,1,3,5,7,10,atomic fraction,%)bulk metallic glasses(BMGs).The investiga-tion used XRD,DSC,SEM,and a universal testing machine for characterizing the alloy system.Results demonstrate that moderate Hf substitution for Cu enhances the glass-forming ability,thermal stability,and compressive ductility of Zr55Al10Ni5Cu30 BMGs.With an Hf content of 7%,the alloy achieves a maximum critical diameter of 12 mm and an expanded undercooled liquid phase interval of 85 K.With an Hf content of 5%,the alloy achieves a critical diameter of 10 mm,an undercooled liquid phase interval of 75 K,and substantially improved compressive plastic strain of 13.3%,thereby enhancing its performance compared with the original composition.Spherical specimens of Zr55Al10Ni5Cu25Hf5 with a diameter of 9.4 mm were prepared using vacuum suction casting,followed by quasi-sealed chamber impact overpressure experi-ments.The results indicate that the critical overpressure velocity of the specimens is approximately 600 m/s,and an impact velocity of 1360 m/s produces a maximum overpressure peak of 0.3291 MPa,where the specimens achieve a peak energy release efficiency of 63.17%.

Ti-Al3Ti brick-and-mortar structure metal-intermetallic laminate (BMS-MIL) composites are significantly better in strength and toughness than conventional Ti-Al3Ti layer structure metal-intermetallic laminate (LS-MIL) composites due to their unique structural features. In this paper, BMS-MIL and LS-MIL composites are compared, and the local strain evolution and fracture behavior of BMS-MIL composites are analyzed by DIC and in-situ tensile tests, and further elucidating the toughening mechanism of BMS-MIL composites. It is found that the number of the strain localized regions increases continuously through strain transfer and redistribution between the continuous network frame structure of ductile Ti and the diffusely distributed Al3Ti platelets, while the peak strain value of the strain localized regions and the area of the regions grow slowly, thus achieving a uniform strain distribution of the materials during the large deformation phase. Due to the large thermal expansion coefficient mismatch between Ti and Al3Ti, there exists a large thermal residual stress in the material, and microcracks first initiate in the diffusely distributed Al3Ti platelets under the combined effect of deformation internal stress and initial thermal stress. Initial microcracks undergo crack deflection, crack branching, crack tip passivation and bridging of the ductile layer during the propagation process, thus relieving the stress concentration at the crack tip and reducing the crack propagation driving force. Subsequently, the cracks gradually propagate into the ductile Ti, and the Ti layers are torn and connected with the cracks in the Al3Ti platelets, resulting in the fracture failure of the composite. Under the combined effect of good strain localization modulation ability and external toughening mechanism, the BMS-MIL composites obtain more excellent toughness and plasticity.

To study the impact energy release behavior, damage effect behavior and space forming behavior of the debris cloud behind the target of La32.5Ce32.5Al10Co25 amorphous alloy spherical fragment, the impact energy release test of an amorphous fragment at different velocities is carried out by using a phi 14.5 mm ballistic gun launching device and a quasi-closed reaction vessel. The impact energy release damage behavior of fragments and the space-forming behavior of debris clouds are analyzed based on the fragment penetrating target fragmentation theory. The results show that the perforation mode of the amorphous fragment penetrating the 2A12 front target is mainly plug damage mode. The average oxygen content of amorphous fragments respectively is 27.73 % and 55.24 % at 793 m s- 1 and 1397 m s- 1. When the impact velocity is 1397 m s- 1, the energy release efficiency of the amorphous fragment is the largest, which is about 65 % and the energy density is 4.7473 kJ g- 1. When the critical activation reaction occurs, the critical impact velocity is 439 m s- 1, and the critical impact pressure P0 is 9.02 GPa. The theoretical model of debris cloud space forming behind the target is established. The evolution law of debris cloud space and impact energy releases damage model of amorphous fragments is obtained.

Syntactic foams characterized by high compression strength and low density are extensively utilized in the aerospace and marine industries. However, the inadequate interfacial strength between hollow glass microspheres (HGMs) and the resin matrix significantly affects the performance of these foams. In this study, we constructed four distinct types of interfacial structures between the HGMs and the matrix using a coupling agent (KH550), graphene oxide (GO), and carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) to enhance the interfacial properties. We investigated the effects of these different interfacial structures on the properties of the syntactic foams, analyzing their failure behavior and enhancement mechanisms. The results indicate that the interfacial structure formed by modifying the HGMs with KH550, followed by coating with MWCNTs-COOH, leads to syntactic foams exhibiting higher compression and flexural strengths of 114.8 MPa and 67.56 MPa, respectively. These values represent increases of 13.6% and 31.0% compared to unmodified syntactic foams. This improvement is attributed to the formation of a rigid-flexible interfacial structure between the HGMs and the matrix, which enables the two components to synergistically enhance performance. This study provides a reference for the development of lightweight, high-strength syntactic foams.

In this paper, a new method for preparing carbon nanotube nickel powder (CNTs-Ni) by grafting Ni particles on the surface of nanotubes was proposed, which included Molecular-Level-Mixing Method and Self-Reduction method. CNTs-Ni reinforced copper matrix composite (CNT-Ni/Cu) was prepared by combining the method with ball-milling and hot-pressing sintering. The surface structure and element distribution of the prepared CNTs-Ni composite powder were investigated, and CNT-Ni/Cu composite materials without added carbon nanotubes and with a carbon nanotube content of 0.1 wt% were prepared using the same ball-milling and hotpressing processes. The microstructure and physical and mechanical properties of the samples were tested and analyzed. The results indicate that the molecular mixing method can achieve the binding of functional groups on the surface of Ni2+and CNTs. CNTs have the self-reducing ability to reduce Ni2+ to Ni element at 950 degrees C in a vacuum environment, achieving the grafting of Ni particles on the surface of carbon nanotubes. The process of ball-milling and hot-pressing sintering dispersed CNTs-Ni evenly in the copper matrix, which effectively improved the hardness and tensile strength of the copper matrix composite. The hardness of the prepared CNTNi/Cu composite was 85.2 HV, the conductivity was 94.1 % IACS, the tensile rate was 18.4 %, and the tensile strength was 232.6 MPa.

Abstract In this paper, the iron-based amorphous/AZ31 microlaminated composites with multilayer structures were successfully prepared by using the vacuum hot-pressing method. The microstructure and chemical element distribution were analyzed, and the mechanical properties and microhardness were tested. Research findings revealed that a thin iron-aluminum intermetallic compound layer was formed between the iron-based amorphous alloy and AZ31, and the interlayers were tightly bonded. The microhardness of the amorphous after the hot-pressing reaction reached 1590 HV and there was a hardness gradient between the AZ31 layer and the amorphous layer. The bending strength reached 516 MPa after hot-pressing temperature at 520°C and the impact toughness was about 6 J/cm2. The fracture behavior was a combination of brittle fracture and ductile fracture. The microstructure and the properties of the laminated composites can be designed by adjusting the process according to the performance needs, which opens up broad prospects for the wide application of amorphous alloys.

Electromagnetic continuous casting technology serves as a significant means for enhancing the casting performance of 2219 aluminum alloy. Investigating the influence of electromagnetic field variations on the solidification process is crucial for studying the microstructure and mechanical properties of electromagnetic cast billets. Through experimental research, variations in the microstructure and mechanical properties were examined for ordinary direct chill casting, as well as three different electromagnetic power casting ingots. The COMSOL software (COMSOL Multiphysics 6.0) was utilized to simulate the temperature and flow field, enabling an explanation of the resulting performance changes. The results showed the effect on electromagnetic continuous casting technology by the electromagnetic field generated by the Lorentz force and melt stirring, improving the melt flow and temperature distribution so that the melt center and the edge of the melt forcible convection were enhanced, thus realizing the tissue refinement, mechanical properties, and Cu element segregation of the improvement. With an increase in electromagnetic power, the distribution of the temperature field was more homogeneous, the segregation phenomenon was more alleviated, and the improvement in mechanical properties was more significant. The optimal microstructure and mechanical properties were achieved at a power of 20.0 kW, with a 74.7% improvement in grain refinement in the center and a tensile strength increase of 30.8%. Additionally, significant improvements were observed in segregation phenomena.

The application of Fe-based amorphous microspheres in high-performance electromagnetic wave absorbing materials is significantly limited by a single loss mechanism. Utilizing interfacial engineering and magneticdielectric synergistic effect is a viable approach to enhance microwave absorption. In this work, FeSiBCuNbZr amorphous microspheres were synthesized using single copper roller melt-spinning method and ball mill method. The finding reveals that the incorporation of SiO2 and TiO2(B) (bronze phase TiO2) shells notably enhances polarization loss and conductive loss. FeSiBCuNbZr@SiO2@TiO2(B) amorphous composites exhibited a minimum reflection loss value of -64.89 dB at a thickness of 2.17 mm and an effective absorption bandwidth (EAB) of 8.08 GHz covering 9-18 GHz at a thickness of 1.9 mm. The exceptional wave absorption performance is ascribed to the combined effect of magnetic loss in the FeSiBCuNbZr amorphous core and dielectric loss from the double-shell structure, while maintaining favorable impedance matching. This work provides a new core-shell FeSiBCuNbZr amorphous composites for efficient electromagnetic wave absorption.

High entropy alloy coatings with a unique microstructure and excellent mechanical properties show significant potential for development in friction-related applications. In this study, the microstructure, phases, hardness and tribological behavior of FeCoNiCrMox x (x = 0, 0.2, 0.5, 1.0) coatings fabricated by HVAF spraying were investigated. The coating changes from a single FCC structure (x=0, =0, 0.2) to a dual phase structure of FCC and sigma (x=0.5, =0.5, 1), accompanied by an expansion in the segregation regions of Cr and Mo elements. The hardness of coatings increased with higher Mo content. Tribology tests were carried out at room temperature using Si3N4 3 N 4 ceramic and GCr15 steel as counterfaces. The results demonstrate that, when paired with GCr15, the wear resistance of the coatings scale proportional with hardness. However, when paired with Si3N4, 3 N 4 , the coating wear rate exhibits an initial increase followed by a decrease. Notably, the FeCoNiCr and FeCoNiCrMo0.2 0.2 coatings exhibited milder friction and wear behavior when in contact with Si3N4 3 N 4 compared to GCr15 steel, attributed to the dominant oxidative wear. This study provides new insights and directions for the design of customized high- entropy alloy coatings based on specific friction conditions.

The brick-and-mortar biomimetic structure Ti/Al3Ti metal-intermetallic laminate (BMSMIL) composites were prepared by vacuum hot pressing. BMS-MIL composites with various Ti volume fractions from 45-71% were obtained by controlling the high-temperature diffusion time of Al-Ti. The phase composition of the BMS-MIL composites was analyzed, and the influence of Ti volume fraction on the microstructure was quantitatively characterized. Quasi-static compression and three-point bending tests were carried out to study the mechanical properties and fracture mechanism of the BMS-MIL composites. The results indicated that, in BMS-MIL composites, Al3Ti appears as polygonal platelets, and Ti fills the gaps between the platelets. With decreasing Ti volume fraction, the size of Al3Ti platelets increased, the number of platelets decreased, and the aspect ratio of platelets first increased and then decreased. The decrease of Ti volume fraction leads to the decrease of mechanical properties of composites. However, as a reasonable and efficient material design strategy, the brick-and-mortar structure ensured that the specific strength of the BMS-MIL composites with load perpendicular to the layer remained stable, with specific strength maintained between 345 and 353 kN m/kg. The compression properties with load parallel to the layer are significantly affected by the platelet's aspect ratio. The sample with 65% volume fraction Ti exhibited the optimal strength, specific strength, and failure strain when compressed parallel to the layer, with a strength of 1347.3 MPa, specific strength of 330.2 kN m/kg, and a failure strain of 6.32%.& COPY; 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

A new Hf-based Hf-Cu-Ni-Al-Ag glassy alloy was synthesized to be formed by copper mold casting. The influence of Ag addition on the properties of Hf48Cu29.25Ni9.75Al13-xAgx (x=0-5at%) glassy alloys was studied by differential scanning calorimeter, X-ray diffractometer, quasi-static compression, and electrochemical corrosion test. The experimental results show that adding Ag can improve the thermal stability and glass-forming ability of glassy alloys. The Hf48Cu29.25Ni9.75Al12Ag1 exhibits the best glass-forming ability with a critical diameter of 12 mm and the highest compressive strength (2363 MPa) among glassy Hf48Cu29.25Ni9.75Al13-xAgx (x=0-5at%). The total plastic deformation of Hf48Cu29.25Ni9.75Al12Ag1 before fracture approaches 4%. In addition, there is a passivation interval of about 3 V for Hf48Cu29.25Ni9.75Al12Ag1 glassy alloy in 1 mol/L H2SO4 solution, which makes the passivation film more stable and increases the corrosion resistance. In 1 mol/L KOH solution, the corrosion tendency and rate decreased with the addition of Ag content, leading to increased corrosion resistance.

The effect of ultrasonic treatment on the microstructure and properties of gray cast iron was studied. The samples were analyzed by metallographic microscope, scanning electron microscope, Brinell hardness tester, electronic universal testing machine, etc. The results showed that ultrasonic treatment could improve the pearlite content in the microstructure. After ultrasonic treatment, the tensile strength of gray cast iron can be improved to 266 MPa, which is 11.60% higher than that of the samples without ultrasonic treatment. Ultrasonic treatment can refine the size of graphite, which can reduce the stress concentration. In addition, the pearlite lamellar spacing can also be reduced, which is the main reason for improving the mechanical properties of gray iron.

2219 aluminum alloy ingot with diameter of φ180 mm was successfully prepared by applying medium frequency magnetic field during semi continuous casting process,and the influence of electromagnetic field on mi-crostructure of ingot as well as microstructure evolution under different homogenization treatment systems were investigated.The results indicate that electromagnetic stirring induced by electromagnetic field can obviously re-fine grains,which promotes the intermittent granular distribution of the intergranular second phase and effectively inhibits dendrite segregation.The homogenization treatment of electromagnetic casting ingot leads to sufficient remelting of the second phase with fine and uniform grains,expanding the homogenization window.Therefore,the reasonable homogenization system of 2219 aluminum alloy by electromagnetic continuous casting was deter-mined as 530 ℃ × 8 h.