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ZrO2-5CrMnMo composites were fabricated by ceramic injection molding in this research. The hardness and wear properties of ZrO2 ceramic layer and 5CrMnMo substrate were investigated. Moreover, physical properties and microstructures of ZrO2 ceramic coatings were studied and the interfaces of composite samples were observed. The results illustrated that the interface was smooth and properly bonded, and it was concluded that the 5CrMnMo substrate ceramic layer could be provided effectively by ZrO2 ceramic coating. Thermal insulation and thermal shock cycle tests were carried out. The heat insulating property of ZrO2 ceramic coating was remarkable, and even better at a high temperature. The composite samples prepared at 1200 °C did not failed until after more than 68 thermal shocks. The main reasons of limiting the application of this composites so far were still the physical and thermodynamic mismatch between ceramics and steel. But the composite samples fabricated by ceramic injection molding showed excellent thermal shock resistance and high bonding strength in this work.

ZrO2-5CrMnMo composite samples were prepared by hot press sintering. When NiCoCrAlY powders were used as the bonding layer and the different mixtures of NiCoCrAlY alloy and 3YSZ (3mol% yttria stabilized zirconia) ceramic powders were used as the transition layers, the connection between zirconia ceramic and 5CrMnMo steel were strengthened. Three composite samples with different structures were fabricated by heat spraying and hot press sintering. Shear and thermal shock cycle tests were conducted to characterize connection strength and thermal shock resistance of these samples. The shear strength reached 95.69 MPa, and the heating shock cycles achieved to the maximum value of 27.7 times. Microstructures and connection interfaces were analyzed by scanning electron microscopy. The hardness and wearing resistance of 3YSZ coat and 5CrMnMo substrate were compared, and the heat insulation property of composite samples were also discussed. It is shown that these composite materials fabricated in this research are benefited to be used as squeeze casting dies.

Composite mold samples used in squeeze casting was fabricated by plasma spraying with 5CrMnMo and 3YSZ, which was shown high bonding strength and good thermal shock resistance. The best parameters with transition coat were explored by mechanical analyses. As results, the transition layer structure made of 75 percent NiCoCrAlY powders showed bonding strength was higher to 34.35MPa and that thermal cycles were up to 46.8 times. The effect of the transition layer was analyzed by microstructures and the failure mechanism of the coating material with a transition layer was discussed. The conclusion was that the physical mismatch and thermodynamic mismatch between the matrix and ceramic layers were the main cause of the failure.

The development of novel cermet composites based on porous ceramics with high porosity, interconnected pore structure and good mechanical property has attracted considerable attention in engineering application. In this work, water-based freeze casting process was employed to fabricate ZrB2-SiC porous ceramic with aligned lamellar-channels structure using PAA-NH4 as the dispersant. The results revealed that the well-dispersed suspension with best rheological behavior was obtained using 1.0 wt% PAA-NH4 at pH 9. The crack-free porous ceramic exhibited small volume shrinkage ranging from 2.59 % to 1.87 %. By varying the solid loading, the fabricated samples displayed a tailored porosity ranging from 76.12% to 59.37% and an excellent compressive strength of 7 MPa to 78 MPa. After oxidation, the samples displayed a decreased porosity and an increased compressive strength. The ZrB2­SiC porous ceramic fabricated in this work will be a promising candidate for the framework of cermet composite.

The research on the ceramic/metal composites with interpenetrating continuous lamellar structure has attracted much interest in structural materials field. In this work, we proposed an innovative approach to fabricate co-continuous ZrB2–SiC/Zn–5Al composites by combining freeze casting with ultrasonic-assisted spontaneous infiltration. The ZrB2–SiC porous ceramic with orderly lamellar channels (30 vol%) was fabricated by freeze casting using ammonium polyacrylate as the dispersant. The effects of ultrasonication duration on the microstructure and mechanical properties of the composites were investigated in detail. Results indicated that the ultrasonication improved the wettability and facilitated the spontaneous infiltration. The composites obtained the excellent comprehensive properties when the duration was 300 s, which can be attributed to not only the sufficient infiltration of lamellar channels but also the longer infiltration distance inside the ceramic walls induced by the ultrasonic capillary and cavitation.

In this paper, 45# steel supports prepared by liquid forging showed excellent performances and the effects of processing techniques on the development of microstructures and mechanical properties of these steel supports were researched. The liquid forging process was simulated and technological parameters were optimized via a ProCAST simulation software. The solidification time, temperature distribution, first principal stress distribution of the 45# steel supports varied with time, temperatures, and position. Two principal parameters, pouring temperature and dwell time, were assessed for their effects on microstructures, mechanical properties, and wear resistance properties of 45# steel supports. Results showed that the optimal pouring temperature of the molten metal and the pressure-holding time were between 1540 °C and 1560 °C and between 35 s and 40 s, respectively. The microstructure, mechanical properties, and fracture behavior of different positions in the support were also discussed, and the central position performed better than the edge because of plastic deformation. Finally, the dynamic solidification process was also investigated and the liquid forging process of 45# steel supports was complex and contained some special metal liquid convection and several plastic deformation stages.

Herein, warm drawing technology assisted by an electric current heating system is proposed to minimize the formation of wrinkles and cracks on the surface of Q390A high-strength steel V-shaped stiffeners during cold forming. V-shaped stiffeners with excellent properties were obtained by elevating the forming temperature and improving the material plasticity. The influence of temperature and tensile rate on the mechanical properties of the Q390A high-strength steel at 400-800°C was investigated. The effects of blankholder force and friction coefficient on the formed parts were simulated and analyzed by the finite element simulation software DYNAFORM. The law of heating and cooling for the formed parts during the forming process was studied through the electric current heating experiments. The forming temperature was controlled from 530 to 720 °C as the current density was maintained in the range from 7.3 to 8.5 A/mm2. Surface oxidation, cracks, sheet warping degree, sectional thickness distribution, mechanical properties, and microstructure of the V-shaped stiffeners formed at 400 to 700 °C were analyzed. The results show that the V-shaped stiffeners formed at 600 °C possess excellent overall properties.

In order to significantly enhance the performance of graphene in metal matrix composites, in situ SiC nanorods were successfully fabricated to enhance graphene nanoplatelets (GNPs)-reinforced Al2024 composite, which was prepared by powder semi-solid processing and friction stir processing. The SiC–GNPs dispersed in the Al matrix uniformly, SiC nanorods were randomly grown on GNPs sheets in any direction, bridging GNPs as well as GNPs and the Al matrix. Meanwhile, the interfacial bonding was effective. The hybrid reinforcement of SiC and GNPs endowed composites with superior mechanical properties and thermal conductivity. The in situ SiC nanorods transfer phonons and reduce phonon scattering effect in the through-plane direction of GNPs, which conducive to heat transmission. The composite exhibits improved mechanical properties, maximum tensile strength and hardness of 589 MPa and 193 HV are obtained, with 1.0 wt% GNPs addition, respectively. The thermal conductivity of composite increases with the content of SiC–GNPs. When the content of SiC–GNPs reaches 1.5 wt%, the composite has significantly enhanced thermal conductivity (224 W m−1 K−1), which is 115% times higher than that of Al2024. Moreover, the effects of SiC–GNPs on the properties were discussed.

The effects of a variable-cavity liquid forging process on the microstructure and mechanical properties of an Mg-5Zn-1Y-0.6Zr magnesium alloy are described based on the results and analysis. The results indicate that the microstructure of the alloy changed clearly during the deformation process. After variable-cavity liquid forging, the dendrites are elongated along the deformation direction. The alloys with different deformation temperatures consist of α-Mg, the Mg-Zn phase, the I-phase (Mg3YZn6) and the W-phase (Mg3Y2Zn3). The I- and W-phases are mainly distributed in the grain boundaries, and the Mg-Zn phase is mainly dispersed in the grains. Most of second phase is broken into fine particles during the variable-cavity forging process. There is high dislocation density in the elongated grains at a deformation temperature of 350 °C, especially near the grain boundaries. Due to the dislocations, there are some tiny subgrain structures (less than 1 μm) formed near the second phase. After the variable-cavity liquid forging process, the subgrain structures did not recrystallize. The mechanical properties are significantly affected by the second phase and size of the grains. The highest tensile strength is 351.5 MPa at a deformation temperature of 350 °C, which is due to retained eutectic pockets. The best elongation is 7.15% at a deformation temperature of 450 °C, which is due to the tiny second phase particles and fine grains.

A ZK61-Y magnesium (Mg) alloy wheel hub was prepared via liquid forging&mdash, isothermal forging process. The effects of Y-element contents on the microstructure and mechanical properties of liquid forging blanks were investigated. The formation order of the second phase was I-phase (Mg3Zn6Y) &rarr, W-phase (Mg3Zn3Y2) &rarr, Z-phase (Mg12ZnY) with the increase of the Y-element content. Meanwhile, the I-phase and Z-phase formed in the liquid forging process were beneficial to the grain refinement. The numerical simulation of the isothermal forging process was carried out to analyze the effects of forming temperature on the temperature and stress field in the forming parts using the software Deform-3D. Isothermal forging experiments and post heat treatments were conducted. The influence of isothermal forging temperature, heat treatment temperature and preservation time on the microstructure and mechanical properties of the forming parts were also studied. The dynamic recrystallization (DRX), second-phase hardening, and work hardening account for the improvement of properties after the isothermal forging process. The forming part forged at 380 &deg, C displayed the outstanding properties. The elongation, yield strength, and ultimate tensile strength were 18.5%, 150 MPa and 315 MPa, respectively. The samples displayed an increased elongation and decreased strength after heat treatments. The 520 &deg, C&mdash, 1 h sample possessed the best mechanical properties, the elongation was 25.5%, the yield stress was 125 MPa and the ultimate tensile strength was 282 MPa. This can be ascribed to the recrystallization and the elimination of working hardening. Meanwhile, the second phase transformation (I-phase &rarr, W-phase &rarr, Mg2Y + MgZn2), dissolution, and decomposition can be observed, as well.

In this work, 7075 Al alloy, a high-strength wrought aluminum alloy with high hot tearing sensibility, was used in the squeeze casting of an asymmetric part. The solidification defects, microstructures and mechanical properties of the part solidified under different forming pressures were studied. Furthermore, the uniformities of the microstructures, mechanical properties and the solidification mechanisms were investigated. Results show that increasing the forming pressure is helpful to improve the liquid/solid feeding for counteracting the particularly serious shrinkage during the wide mushy zone of 7075 Al alloy. Therefore, the solidification defect can be avoided. Moreover, increasing the forming pressure is helpful to not only obtaining fine equiaxed grains, but also diminishing the intergranular segregation of alloying elements. With the increasement of forming pressures, the strengths of the part increased, along with the decreases in the ductile due to the work hardening resulted from the serious solid feeding. The microstructures and mechanical properties are impacted by the solidification rate of the melt at different regions. When the forming pressure was 150 MPa, fine microstructures and excellent mechanical properties were obtained. The uniformity of the microstructures and mechanical properties are dominated by the solidification location sequence of the melt. Further on, it is determined by the thermal gradient of the melt at different locations. For 7xxx series alloys, more solid feeding is needed for counteracting the serious shrinkage at the first solidified regions, causing a work hardening and associated strengths increasements. A near uniform part thickness and direct feeding loads are appreciated to improve the uniformities. In this work, the optimal tensile properties tested in the part were tested to be as follows: the yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) are 345.5 MPa, 483.2 MPa, and 7.6%, respectively. The UTS uniformity is tested to be 86.4%.

A human torso finite element model with high bio-fidelity was developed to study the behind armor blunt trauma (BABT) of pistol cartridge on human torso with bulletproof composite structure (BCS) and the effect of buffer layer (expandable polyethylene, EPE) on BABT. The bulletproof structure was made of multilayered composite of aluminum alloy (AlSi10Mg) and thermoplastic polyurethanes (TPU), and the ANSYS/LS-DYNA software was used to simulate the blunt ballistic impact process of pistol cartridge on human torso. Results indicated that the BCS could resist the shooting speed of 515 m/s without being broken. During the process of pistol cartridge shooting the BCS, the energy of pistol cartridge was transmitted to the human organs through the BCS, thereby causing human injury. Moreover, the mechanical response parameters of various organs were determined by the distance between the human organs and the impact point. The sternal fracture and liver rupture were not produced based on the threshold stress of sternum and liver injury, no matter whether the buffer layer was added or not. According to the Axelsson injury model, a slight to moderate injury was created when there was no buffer layer, but the injury level was trace to slight caused by the buffer layer with thickness of 1.0 mm, and the buffer layer with thickness of 2.5 mm and 5.0 mm caused subtle BABT. It was concluded that the buffer layer could effectively reduce the BABT, and the reduction was related to the thickness of the buffer layer. This study reveals the mechanism of the BABT, which can provide a theoretical basis for the design of the bulletproof structure and the evaluation of structural bulletproof performance and protection performance.

The formation process of Al3Ti was studied based on the in-situ reaction between globular solid Ti powders with almost uniform size and 2024 Al melt under ultrasonic vibration. The microstructures of the Al3Ti/Al composite were examined at different reaction time. The reaction mechanism was analyzed based on the phase diagram and empirical reaction kinetics. Moreover, the effects of ultrasonic vibration on the formation of Al3Ti were discussed. The results show that the Al3Ti formed a layer around the unreacted Ti particle and was ruptured as the reaction continuing. An empirical reaction kinetics model of in-situ Al3Ti was established. The kinetic exponent n is determined to be 0.86, which is much higher than that of the standard diffusion-controlled growth (n = 0.5). The ultrasound assisted reaction follows an interface-controlled growth which means a higher reaction rate. The comprehensive effects of instantaneous pressure, high-intensity shock waves and local high-temperature caused by acoustic streaming and cavitation, are responsible for the high reaction rate and fine Al3Ti particles during the reaction process under ultrasonic vibration.

Taking carbon series conductive coatings as the research object, research on a modificatory filler was carried out to achieve higher electrical conductivity. Under the condition of this paper, the conductivity of the modified carbon black was improved, while the performance of the modified graphite was not obviously improved. The conductivity and dispersion of the modified carbon fibre were both improved. Analysing the impact of the additive on the performance of conductive coatings in which carbon black accounted for 10%, the conductivity was best when the weight of the tetra-butyl titanate was 1% of the filler. Adding an anti-settlement agent also improved the performance of the conductive coatings, and the best consumption was about 0.6% of the weight of the filler.

A pyrotechnical battery is successfully prepared, including an anode and cathode having pyrotechnic charges with Zr, CuO and asbestos. The anode and cathode are separated by a separator formed from LiF, ZrO2, and a fibrous sponge. A digital phosphor oscilloscope (DPO) is used to analyze discharge characterization of the pyrotechnical battery. Then the properties of the electrode materials are characterized by EDS, SEM and a temperature recorder, respectively. The discharge mechanism and safety characteristic are also discussed. The results indicate that the combustion temperature of electrode materials is determined as 1 500.6 °C according to thermometry analysis (the case temperature of the battery is lower). The combustion product is identified as ZrO2, Cu2O and Cu by X-ray diffraction (XRD). When the diaphragm is completely melted, Li+ migration and an embedded-based conductive process are formed. Then an electromotive force will immediately reach to the maximum. The discharge performance of the pyrotechnical battery then takes on stability. The electromotive force is up to 2.29 V, and that discharge time continues for more than 18 s. The current density in the small area (less than 2.88 Acm−2) is most effective. The conversion efficiency of electric energy is 96%. The pyrotechnical battery is very safe for the production and use processes.

In order to study the influence of the environmental humidity on thermal decomposition of pyrotechnic compositions, this experiment has been set up with artificial simulation environment of high humidity. The thermal analysis experiments have been done by using the integrated thermal analyzer. Thermal decomposition curves in the high humidity environmental conditions and the normal environmental conditions have been obtained. And the starting temperature, peak temperature, as well as the change rules of the activation energy in the decomposition reaction have been gotten, which shows that the thermal safety of the pyrotechnic compositions in the high humidity environment is lower.

Pyrotechnical battery is successfully prepared, including an anode and cathode having pyrotechnic charges with an excess of fuel-anode and an excess of oxidation agent cathode (Zr, CuO and asbestos), the anode and cathode being separated by a separator formed from LiF, ZrO2 and fibrous sponge. Main performance indexes system of pyrotechnical battery is put forward and tested under the premise of appropriate mass and corresponding size, such as discharge voltage, discharge time, activation time, excitation time, internal resistance, combustion temperature and storage life. The results show that pyrotechnical battery of Zr/CuO system can basically meet application requirements. Activation time is usually about 0.2 s. Discharge voltage is about 1.96 V and the discharge time is up to 13.8 s or more. The internal resistance keeps a low fixed value (0.47Ω , for example). Combustion temperature of pyrotechnic composition can reach 1500.6 °C (the case temperature of battery is lower) to ensure that electrode and separator is adequately melted, consequently, the internal resistance is reduced, and achieving satisfactory discharge effect.

Ultrasonic vibration have positive effect on formation of in-situ TiAl 3 /7050Al composites, the role of ultrasound in the reaction process was described systematically. The best solution-aging treatment parameters were discussed and effects of the selected treatment on the resultant microstructure and mechanical properties were investigated. The results show that ultrasonic vibration not only promote the reaction process, but also result in significant spreading particles fallen off from the reaction interface, therefore creating a finer and homogeneous distribution of TiAl 3 particles in the composite. In solution process, the skeleton second phase dissolve into matrix with increasing temperature and holding time, the transformation is more sensitive to solution temperature. Residual second phase transform into finer-size rod or discoid shape and a large amount of finer phase (MgZn 2 and CuAl 2 )precipitates after aging-treated. As a result, the strength, hardness and elongation of the composite are slightly increased after using ultrasonic vibration and significantly increased after solution-aging treatment.