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This study explores the stability of Al–Si–Ca–Mg-Sc melt foams and investigates the melt foam filling process and the dynamic evolution of pore structures in the fabrication of foam aluminum profiles using the melt transfer foaming technique. The results show that Al–Si–Ca–Mg-Sc melt foam maintains high porosity and a stable pore structure even after 30 min of foaming, without any signs of boundary rupture or destabilization. This stability is attributed to the increased viscosity from finely dispersed second-phase particles, which hinder the growth, coalescence, and drainage of the melt foam. Regarding melt foam filling, enhanced filling capability is achieved by elevating the foaming temperature, extending the foaming time, and increasing the TiH2 addition. The melt foam exhibits a smooth flow from the lower part of the mold to the corners, completing the filling process with well-defined edges in the profile. During lateral movement for filling, a gradual increase in porosity, a decrease in pore number, and a slow enlargement of pore size and standard deviation along the lateral (x-axis) are observed. This is due to the slower liquid phase flow compared to the gas phase, resulting in bubble coalescence. After filling is complete, this phenomenon improves, contributing to a slow and stable evolution of the pore structure.Under optimized conditions of 1.4 wt% TiH2 addition at 600°Cfor 9 min of foaming with Al–Si–Ca–Mg-Sc alloy melting, we successfully fabricated foam aluminum profiles with complete filling, a porosity of 81.5%, an average pore size of 2–3 mm, and a uniform pore structure.

This study investigated the influence of Sb addition on the microstructure, thermal behavior, mechanical properties, and interfacial evolution of SAC305-2Bi-xSb/Cu solder joints. Compared with the SAC305-2Bi alloy, the melting temperature and pasty range slightly increased with the increasing of Sb content from 0.2 to 2.0 wt.%, while the undercooling temperature decreased. The research revealed that with the addition of Sb element, the grain size of β-Sn is refined. When the content of Sb is 0.5 wt.%, the grain size of β-Sn reached minimum (19.91 μm). Compared to the SAC305-2Bi alloy, the ultimate tensile strength of SAC305-2Bi–2Sb alloy is increased by 30.10%, contributed to the Sb solid solution strengthening effect and the refinement of β-Sn. With the addition of Sb, the thickness and growth rate of the interface is reduced gradually. The uniform solution of Sb and Sn can significantly inhibit the diffusion rate of Cu atoms and Sn atoms at the interface. The SAC305-2Bi-xSb alloy system has low melting temperature, superior mechanical properties, and reliable solder joints for service. Therefore, it is a potentially reliable lead-free solder for high-stability connections in automotive electronics, communications electronics, and medical devices.

Developing reticular reinforcement and heterogeneous microstructure remains persistent challenges in one-dimensional carbon nanotube (CNT)-Cu system. We herein fabricated dual-heterostructured Cu composite by diazotizing CNT into cross-linked (CL) networks and achieving bimodal grain distribution. The CL-CNT networks uniformly dispersed in Cu matrix, forming strong C–N/O–Cu covalent bonds at the interfaces and effectively retarding grain growth to create ultra-fine grain (UFG) regions around them. The CL-CNT networks/UFG regions, along with the surrounding coarse grain (CG) regions, resulted in a remarkable synergy between mechanical and electrical properties within the composite. Systematic analysis indicates that CL-CNT network acts as a whole to bear loading, remarkably enhances the load-transfer strengthening and promotes the dislocation accumulation around the interface. Meanwhile, hetero-deformation between “hard” CL-CNT networks/UFG regions and “soft” CG regions lead to extra-strengthening and hardening associated with strain partitioning, generation of geometrically necessary dislocation (GND) and strain delocalization. In-situ tensile test further reveals that CL-CNT/Cu with dual-heterostructure introduces the extra-toughening via crack bridging and deflection mechanisms. Besides, CL-CNT network with the robust interface is considered to reduce the interfacial inelastic scattering and provide additional paths for electron transport, accounting for the high electrical conductivity. This work highlights the importance of configuration design of reinforcement in tailoring heterostructured metal matrix composites (MMCs) with outstanding comprehensive performance.

In this study, Cu–9Ni–6Sn-xCr alloys (x = 0, 0.3, 0.6, or 1.0) were designed and prepared. The influence of Cr content on the microstructure, the precipitation behavior, and the mechanical properties of the alloys was systematically investigated. The results show that the Cu–9Ni–6Sn-0.6Cr alloy exhibits outstanding mechanical properties and higher level electrical conductivity after aging at 400 °C for 8 h: The peak-aged hardness reaches 323.6 ± 8.4 HV, with a tensile strength of 876.4 MPa and an electrical conductivity of 12.59 ± 0.33% IACS. These excellent comprehensive properties of Cu–9Ni–6Sn-0.6Cr alloy are attribute to the refinement effect and the precipitation of DO22 phase within the Cu matrix grains. Further analysis reveals that the addition of an appropriate amount of Cr refines the microstructure of the alloy and promotes the precipitation of the DO22 phase. At the same time, Cr also suppresses the precipitation of the DO3 phase at grain boundaries, achieving an excellent combination of plasticity, electrical conductivity, and strength. This work suggests that the potential application prospects of Cr in the multi-component design of Cu–Ni–Sn alloy, and the addition of 0.6 wt% Cr can achieve good strengthening effects and provide outstanding comprehensive performance for Cu–Ni–Sn alloys.

In this work, an in-situ boride-reinforced Ti6Al4V compositionally graded material was prepared successfully by spark plasma sintering (SPS), and exhibited a good potential for military application because of its stepwise transition properties from a high-toughness end to a high-strength end along the thin-thickness direction. Microstructure characterization shows the chemical gradient ranged from 0 to 30 wt% TiB2 along the thickness direction, which was correlated with increasing micro-hardness values ranging from 565±5HV to 1270±5HV, respectively. The strength-toughness matching mechanisms of the gradient composites with different compositional gradients were discussed based on the static compression experiments and the dynamic Hopkinson compression rod experiments. The primary phases of the gradient composites included the α-Ti phase, β-Ti phase, remained TiB2 and in-situ formed whisker-like TiB phases. The composites with a compositional gradient of G84 (0, 0, 15, 30 wt%) exhibited the best impact resistance which achieved a good balance of high toughness and strength, and exhibited a compressive strength of 2148±5 MPa and a good elongation of 20 ± 0.5%. The strength-toughness matching mechanisms can be explained by the dispersion strengthening effect due to the presence of the in-situ formed TiB phase, and the consumption of more fracture energy by dislocation defects, which can prevent the crack propagation. Moreover, the pull-out of the whisker-like TiB phases toughened the gradient composites furthermore. This research demonstrated a reliable method for preparing TiB2/Ti–6Al-4Vgradient composites with high-impact resistance.

The hot deformation behavior of the solutionized Cu–15Ni–8Sn alloy is investigated by hot compression tests at temperatures of 750–900 °C and strain rates of 0.001–1.0 s−1. The flow stress curves of the alloy are analyzed, and the constitutive equations are developed to predict the flow behavior of the alloy. In addition, the optimal deformation conditions are proposed through the constructed hot processing map and microstructure analysis, revealing the impact of the deformation mechanism under different deformation parameters on the microstructure evolution. The results show that temperature and strain rate have a great influence on the hot deformation of the alloy. The strain-compensated constitutive equation can well predict the peak flow stress of the alloy, with a correlation coefficient of 0.993 between experimental and predicted values. The high power consumption region is mainly caused by dynamic recovery and partial dynamic recrystallization, while flow localization is the main reason for the appearance of the unstable region. The optimum hot processing conditions for the alloy are at a temperature range of 750–780 °C and the strain rate is 0.001–0.0025 s−1.

The graphite-reinforced epoxy resin composite (Gr/EP) is considered one of the promising solid lubricating materials. However, the low thermal conductivity and correlated poor wear resistance cause limitations to its tribological applications. With the expectation to improve the thermal conductivity and wear property, carbon nanotube (CNT)-reinforced copper foams (CNTs/Cuf) are introduced as 3-dimensional skeletons to reinforce Gr/EP composites. Herein, comprehensive testing was conducted to assess the wear resistance, thermal conductivity, microstructure, and wear morphology of the composites. The results revealed that incorporating Cu or CNTs/Cu foams into the Gr/EP matrix significantly enhanced thermal conductivity and wear resistance, with only minor elevation of the friction coefficients, which showed a consistent decline trend with increasing CNTs contents. Notably, with the CNT content of 0.159 wt%, the composites reached the favorable combination of a 25.4 % improvement in thermal conductivity and a 34 % reduction in wear rate compared to pure copper foam-reinforced Gr/EP composites.

The effects of Ag addition on the microstructure of Sn–9Zn alloy and its corrosion behaviour in neutral and static 3.5 wt% NaCl solutions were investigated using surface characterization techniques and electrochemical techniques. The results show that in Sn–9Zn-xAg alloys, Ag reacts with Zn to form AgZn3 intermetallic compounds (IMCs), which refined the microstructure of the alloys and changed the corrosion mode of the alloy surfaces from pitting corrosion to surface corrosion. The addition of Ag effectively improved the corrosion passivation film structure and electron transfer characteristics of the alloy, increased the self-corrosion potential (Ecorr) and reduced the self-corrosion current (Icorr), thus improving the corrosion resistance of the alloy. The study explained and verified the corrosion mechanism of the alloy from both experimental and theoretical perspectives. It is concluded that Sn–9Zn-0.4Ag alloy shows relatively the best corrosion resistance.

Insight into the well-balanced mechanical-electrical properties of copper composites is requisite to provide an understanding for the development of novel structure–function integrated materials. In this study, the multi-dimensional hybrid reinforcements, carbon nanotube and zero-dimensional carbonized polymer dots (abbreviated as: CNT + CPD), were incorporated within copper matrix via spraying pyrolysis dispersion and segmented ball milling routes. A novel strategy was developed to simultaneously introduce intragranular CPD and intergranular CNT by controlling the spatial configuration. Characterization results show that the dispersibility and interface wettability of CNT-Cu were improved by the spraying pyrolysis. Intragranular CPD facilitated the trapping and accumulation of dislocations inside grain interior, which enhanced the strain hardening capability. 3.0 vol% CNT-CPD/Cu composites achieved good strength-plasticity compatibility (410 MPa and 19.8 %, i.e., 146.6 % and 139.3 % of the CNT/Cu composites, respectively). Meanwhile, composites had also displayed good electrical conductivity (96.5% IACS), which was attributed to the creation of conductive graphitic channels locally around intragranular CPD and produced a potent electric field with little charge loss. This work presented an effective route for the design of advanced copper composites and demonstrated potential in applications as progressive multi-functional materials.

The hot deformation behaviour of an as-cast Cu–20Ni–20Mn alloy was investigated by isothermal compression tests in a TA-DIL 805 phase change thermal expansion instrument with a temperature ranging from 800 to 950 °C and a strain-rate ranging from 0.001 s−1 to 1 s−1. The results showed that Cu–20Ni–20Mn presented a stress drop at the beginning of the strain, and the flow stress decreased with increasing temperature and decreasing of strain rate. In particular, the hot deformation activation energy was determined to be 277.958 kJ/mol. The hot compression constitutive equation was established, and the processing maps of the alloy were constructed. The stress-strain values predicted by the proposed model were coincident with the experimental results, which confirmed that the deformation principal equation gives an accurate and precise estimate of the flow stress in Cu–20Ni–20Mn. The established processing maps and microstructure analysis determined the rolling process parameters in which the optimum range of temperature for the hot-working deformation of the as-cast Cu–20Ni–20Mn alloy is 810–900 °C with a strain rate of 0.001–0.002 s−1.

Reinforcement architecture and interfacial structure are two key factors affecting the performance of composites. Herein we attempted to achieve a comprehensive improvement of mechanical properties of carbon nanomaterials (CNMs) reinforced Cu matrix composites by means of reinforcement structure construction and interface structure optimization. Graphene oxide (GO) and acid-treated carbon nanotubes (AT-CNTs) were self-assembled into a GO-CNT hybrid structure through an ultrasonic mixing method, and then used as reinforcement of Cu matrix composite through the powder metallurgy method. The strengthening efficiency of GO-CNT hybrid was significantly higher than that of individual CNTs or GO, which could be attributed to the stable interconnected architecture of GO-CNT hybrid formed through sp3 hybridized C–C bonds and the larger interfacial area between them and Cu matrix. In addition, aiming at the issue of poor interfacial adhesion between the GO-CNT hybrid and Cu matrix, TiC nanoparticles were introduced onto the surface of GO-CNT hybrid through a pressureless spark plasma sintering strategy. The TiC nanoparticles can improve the interfacial wettability and optimize the interfacial bonding state. TEM results confirmed a semi-coherent interfacial lattice matching relationship between TiC nanoparticles and Cu matrix, which was conducive to forming robust interfacial bonding. Through the construction of hybrid reinforcement and the introduction of nanosized interfacial TiC, the GO-CNT hybrid reinforced Cu matrix composite has obtained ultra-high strengthening efficiency, and exhibited satisfied combination of strength and ductility. This study can provide a referential strategy for the comprehensive performance optimization of CNMs reinforced metal matrix composites.

The thermo-mechanical and failure behavior of the burning-free Al2O3 –C–SiO2 slide gate plate materials during the steel casting process are investigated. Firstly, the instantaneous coefficient of thermal expansion and the Young's modulus of the slide gate plate materials with different component contents at high temperature are measured. Secondly, a material constitutive model and a concrete damage plasticity mode are established based on the experiments, and adopted to simulate the failure behavior of the burning-free Al2O3–C–SiO2 slide gate plate during casting based on Finite Element Method (FEM) analysis. Results show that temperature gradient in the slide gate plate near the casting hole increased significantly and had a significant influence on cracking. The area near the casting hole of the slide gate plate is under tensile stress conditions, and then changes towards compressive stress conditions. Under those severe thermal stress conditions, crack formation is evaluated and an optimized composite structure of the slide gate plate combining advantages of reducing the risk of cracking and extending the service life is proposed. Moreover, the thermal shock test further verified that the microcrack extension was significantly alleviated due to the SiC distributed in whisker form and formed an interlocking structure in material. This work provides a reliable theoretical and experimental basis for the design and optimization of high performance Al2O3–C–SiO2 slide gate plates.

In this paper, inhomogeneous copper matrix composite with carbon nanotube reinforced copper foam (CNTs/Cuf) as the three-dimensional (3-D) skeleton is designed to overcome the paradox between strength and ductility or conductivity. The open cell composite foams with uniformly embedded CNTs are filled with dense copper phase in the foam pores by spark plasma sintering (SPS) to form the inhomogeneous composites. The inhomogeneous composite reinforced with CNTs/Cuf shows a combination of high electrical conductivity (93.4% IACS), tensile strength (366.7 MPa), and fracture elongation (31.78%) with a quite low CNTs content (0.2414 vol%). In addition, the polarization curves and AC impedance (EIS) tests show that the best corrosion resistance is achieved with the CNTs content of 0.2414 vol%, and the corrosion rate is reduced by 71.9% and 49.1% compared with the Cu and Cuf®Cu samples, respectively.

As-cast CrCoNi Medium Entropy Alloy (as-casted MEA) was obtained by vacuum arc melting. The as-casted MEA was rolled 3 times at the temperature of liquid nitrogen (77 K), the sum of the total deformation was 50%. Then, the rolled CrCoNi Medium Entropy Alloy (as-rolled MEA) were annealed with different parameters, the annealing parameters were 923 K/30min, 973 K/30min and 1073 K/30min respectively. The experimental samples were characterized by uniaxial tensile test at room temperature, electron back scatter diffraction (EBSD) and transmission electron microscopy (TEM). The tensile test results showed the CrCoNi MEA was deformed by Liquid Nitrogen rolling, the tensile strength increased from 421 MPa to 1312 MPa, but the elongation was only 7.4%. The as-rolled MEA annealed at moderate temperature and short time, the ductility of the CrCoNi was improved significantly. When the as-rolled MEA annealed at 1073 K/30 min, the elongation of CrCoNi increased to 65.3%, while the tensile strength maintained 800 MPa. The EBSD and TEM results showed that the CrCoNi MEA was deformed by Liquid Nitrogen rolling, there were a lot of high density dislocation regions in the alloy. At the same time, a large number of bunches of stacking faults (SFs), intersected SFs and deformation twins (DT) were found in the rolled MEA. The EBSD and TEM results also showed that when the CrCoNi MEA was annealed, a large number of type B and type C annealing twins and 9 R structures were found in the alloy. The growth of annealing twins were achieved by the mechanism of grain boundary migration caused by stacking faults annexation. After annealing, the transformation of FCC→9 R structure was occurred, and the 9 R structure caused more boundary nucleation of annealing twins. The annealing twins and 9 R structure played a key role in improving the ductility of the annealed CrCoNi MEA. Adopt the technology of moderate temperature combining short time annealing process, can effectively control the properties of CrCoNi MEA.

With a unique cellular structure to enhance the multi-reflection and multi-absorption properties of electromagnetic waves, metal foam is considered a new type of electromagnetic shielding material that can also be used for lightweight structural applications such as energy absorption and shock attenuation. This work introduces reduced graphene oxide (RGO) to reinforce Cu foam for the purpose of improvement of the foam's mechanical and electromagnetic shielding properties. After the preparation stage of the electrodeposition and heat treatments, the RGO was observed to uniformly disperse in the Cu foam matrix and nano-sized Cu2O particles formed at the interface. This resulted in improved mechanical properties and electromagnetic shielding performance compared to the pure Cu foams. The primary shielding mechanism was deduced as absorption loss.

Ammonia (NH3), as main industrial gas emissions, are extremely harmful to the human beings. So the detection of NH3 concentrations in special environments at room temperature (25 °C) is essential. Herein, the composite MXene Ti3C2Tx-TiO2-CuO was successfully prepared by one-step in-situ oxidation method using Cu(NO3)2·6H2O as a precursor. The morphology of Ti3C2Tx-TiO2-CuO shows layered accordion-like structure. Ti3C2Tx-TiO2-CuO sensor exhibits improved NH3 gas sensing response of 56.9 toward 100 ppm NH3 at room temperature under ultraviolet (UV) light exposure, which is 89.8 % higher than that of pristine Ti3C2Tx material. The improved gas sensing performance is attributed to the irradiation of UV light, the retention of Ti3C2Tx layered structure and the construction of TiO2-CuO heterojunction. Further, the possible gas sensing mechanism of the material was proposed and discussed.

The preparation method of advanced ceramics that serve as target materials, has been the key challenge to produce high quality thin film transistors (TFTs) with the desired properties. In this study, a novel two-step sintering (TSS) process was successfully applied to fabricate indium gallium zinc oxide (IGZO) ceramics. The sintering behaviour of the IGZO compacts was investigated in detail and it was established that the first step optimum temperature should be in the range of 1400–1500 ℃, while for the second step should be 1350℃ with a dwell time of 12 h. Using this method, the relative density, average grain size and resistivity of the IGZO ceramics could reach 99.5%, 4–5 μm and 2.31 mΩ⋅cm, respectively. The corresponding IGZO thin films produced from the ceramic through sputter deposition had an average transmittance of over 88% and a low resistivity of 3.56 mΩ⋅cm. These excellent properties suggest that TSS has considerable potential as a viable approach for the preparation of ceramic target materials, which find application in the fabrication of TFTs.

The intrinsic properties and the damage behavior of powder metallurgy (P/M) connecting rod preform have significant effects on its metal flow behavior during flashless forging into its final complex shape with substantial densification. The P/M material constitutive equation were established using isothermal compression tests, and then used to study the metal flow behavior of a P/M connecting rod preform during flashless forging based on finite element modelling (FEM). Moreover, the preform geometry was designed based on these metal flow mechanisms. Experiments and flashless forging of P/M connecting rod preforms were performed in order to verify the accuracy of the simulations. The simulated results are well consistent with the experimental results. Results showed that the shank is much more prone to cracking due to the higher deformation rate and the faster cooling rate. The optimal dimensions of the P/M preform were obtained. When the preform geometry are optimized, the average density of the connecting rod increases homogeneously, and becomes superior to that of the original shape. This work suggests that the geometry of the preform can be designed efficiently based on our models. This work can help to derive a P/M connecting rod preform optimization methodology, which can offer the possibility of improving the quality of the connecting rods efficiently. Keywords: Connecting rod, Numerical simulation, Optimization, Powder metallurgy

Interface optimization is the most important and eternal research issue in preparation of the metal matrix composites (MMCs). For nano sp2-carbon material (NSCM)/metal composites, interfacial precipitates are usually formed intentionally or unintentionally, however, the effect of the interface structure and precipitates on the electron transport properties is still unclear, which is especially important for Cu-based material due to the electronic and electrical applications. In this paper, a series of interface models were constructed based on the transmission electron microscopy (TEM) observation of NSCM/Cu composite and calculated through density functional theory (DFT). The geometric structure, interfacial charge transfer, work function, Bader charges, electron differential density distribution and electronic density of states of Cu/graphene (GR), Cu2O/GR, Cu/Cu2O and Cu/Cu2O/GR interfaces were discussed in detail, we conclude that the Cu2O precipitates at the Cu/GR interface can reduce the average distance and increase the binding energy between Cu and GR. Besides, the formation of Cu2O can improve the electronic transport between Cu2O and copper instead of the weak binding of the Cu and graphene, but Schottky barrier at the interface remains an obstacle need to be overcome. The results can provide reference for the interface design of MMCs and the improvement of the composite properties.