As a commonly used metal material, copper is limited in its application due to its low strength. Because of its excellent comprehensive properties, graphene has attracted wide attention as a potential reinforcement. Graphene reinforced copper matrix composites combine the great properties of both copper and graphene, and have become an research hotspot. The preparation processes and comprehensive properties of graphene reinforced copper matrix composites are introduced. The characteristics of various preparation processes, strengthening mechanism and configuration design are emphatically discussed, and the improvement approaches to solve the two main technical difficulties of weak bonding of composite interface and difficult dispersion of graphene are summarized. Finally, the preparation process of graphene reinforced copper matrix composites is prospected.

Selective laser melting (SLM) is one of the most widely used metal additive manufacturing techniques. Many defects are inevitably produced in the SLM formed parts, including pores, surface layer powder spheroidization, cracks and so on. The formation of defects not only affect the smoothness of the forming process, but also damage the internal integrity of the part and reduce its serviceability. The main characteristics of three defects including pores, surface layer powder spheroidization and cracks in SLM formed 316L stainless steel parts are reviewed. The formation mechanisms and influencing factors of these three defects are summarised, and the main measures to control the defects are proposed. Finally, future research directions are put forword.

IN718 nickel-based superalloy powder was spreaded at different scraper moving speeds (28.23, 63.55, 91.11, 125.25 mm·s^-1), and the powder layer thickness was 0.3, 0.5, 0.7, 0.9 mm, respectively. The powder at different positions with the same volume of the powder layer was collected by a self-made device for testing powder uniformity and weighted. The influence of the scraper moving speed and the powder layer thickness on the powder spreading uniformity was studied by calculating mass standard deviation. The results show that the mass standard deviation of the powder layer increased with the increase of the scraper moving speed or the powder layer thickness, indicating the powder spreading uniformity became worse; the scraper moving speed had a greater effect on the powder spreading uniformity. The optimal process parameter combination to obtain the best powder spreading uniformity was listed as follows:scraper moving speed of 28.23 mm·s^-1 and powder layer thickness of 0.3 mm.

High entropy alloys have great development potential in industry with the advantages of high strength,high hardness and corrosion resistance. The phases of typical high entropy alloys include solid solution phases, such as face-centered cubic (FCC) phase,body-centered cubic (BCC) phase and hexagonal close-packed (HCP) phase, and amorphous phases. The unique phase structure has an important influence on mechanical behaviors of high entropy alloys. The mechanical behaviors of high entropy alloys with different phase structures are reviewed, and the research progress on phase structure prediction methods of typical high entropy alloys, including empirical rule, CALPHAD method, first-principles calculation and machine learning method, are summarized. The future development direction of phase structure prediction of high entropy alloys is given.

The creep-fatigue tests with load holding at maximum stress controlled by load with different stress ratios (0.2-0.4) and holding times (0.3-1.5 h) of X12CrMoWVNbN10-1-1 steel at 620℃ were carried out, and the creep-fatigue interaction and fracture mechanism of the steel were analyzed. The results show that the creep-fatigue life of the test steel had exponent relation with the holding time. The longer the loading time, the less the influence of stress ratio on creep-fatigue life. The creep fatigue interaction factor defined from the view of strain could well reflect the interaction between the true stress-true strain hysteretic curve and the creep fatigue life in the stable stage. The creep-fatigue fracture mode of the test steel was ductile fracture. When the holding time was short of 0.3, 0.5 h, the fatigue damage suppressed creep damage, and the damage was mainly controlled by cyclic fatigue load; the dimples on the fracture were caused by crystal boundary slide controlled by fatigue. When the holding time was long enough of 1.0, 1.5 h, the fatigue damage promoted creep damage, and the damage was mainly controlled by time-related creep load; the dimples on the fracture were caused by detachment of inclusions or second phase particles.

On the basis of the chemical composition of HR3C steel, the mass fractions of niobium element were adjusted to 0.5%, 0.8% and 1.1%, respectively. The ingot samples with the three components were obtained by melting, and then subjected to hot rolling, homogenization annealing at 1 200℃, solid solution at 1 200℃, and aging at 750℃ for different times (0-2 000 h). The effects of niobium content on the microstructure, grain size and hardness of the test steel were studied. The results show that increasing the niobium content could increase the content of undissolved MX phase in the solid solution test steel and reduce the grain size. During aging at 750℃, increasing the niobium content could promote the precipitation and coarsening of σ phase at grain boundaries and inside grains, and improve the hardness. When aging for 2 000 h, the niobium content had little effect on the size and distribution of grain boundary precipitates, but had some influence on the size and shape of intragranular precipitates; the test steel containing 1.1wt% niobium had a relatively small number of strip-like intragranular precipitates.

Fe-2%Cu-0.4%C iron-based powder metallurgy material was boronized at 950 ℃ for 5 h by solid powder boronizing method with a boronizing agent containing CeO₂. The effects of CeO₂ addition (0,2%, 4%, mass fraction) on the microstructure and friction and wear properties of the boronizing layer were studied. The results show that the boronizing layer with different addition amounts of CeO₂ had a single Fe₂B phase. With the increase of CeO₂ addition, the surface roughness of the boronizing layer increased, and the thickness, hardness and wear resistance increased first and then decreased. When the mass fraction of CeO₂ was 2%, the thickness and hardness of the boronizing layer were the largest, about 144 μm and 58.0 HRC, respectively. At this time, the surface integrity of the boronizing layer was relatively good, the amount of wear was the smallest, about 0.008 g, and the wear resistance was the best.

The dry and wet two-stage continuous rolling contact wear tests were carried out on U75V rail samples without surfacing and with local surfacing. The rolling contact characteristics and wear behavior of the two rail samples were compared and analyzed.The results show that the adhesion coefficients of the two rail samples were both about 0.60 in the dry wear stage, and decreased sharply to about 0.25 into the wet wear stage; the adhesion coefficient of the local surfacing rail sample in the dry wear stage was slightly higher than the un-surfacing rail sample, and the wet wear stage was the opposite. The surfacing layer of the local surfacing rail sample mainly consisted of martensite and had the highest hardness. The wear surface damage of surfacing layer was slight, and no obvious cracks and plastic deformation were found. The heat affected zone was composed of ferrite, pearlite and martensite and the hardness was in the middle. After wear, the surface roughness of the heat affected zone was the largest, the plastic deformation was large and there were many cracks with large expansion angles. The non-surfacing zone was mainly composed of pearlite and the hardness was the lowest. After wear, the surface of the non-surfacing zone was flat, and obvious plastic deformation and a small amount of cracks were found.

The 4Cr5Mo2V steel was quenched at 1 000-1 090 ℃. The tempering hardness of the test steel quenched at the same temperature was adjusted to 55,52 HRC by tempering twice at different temperatures, and the effects of the quenching temperature and tempering process on the microstructure, impact toughness and high temperature (350 ℃) wear resistance were studied. The results show that when the tempering hardness was the same, too high or too low quenching temperatures would reduce the toughness of the test steel and aggravate the peeling of the wear surface material, thereby reduced the wear resistance. Under the same tempering hardness, the toughness and high temperature wear resistance of the test steel quenched at 1 030 ℃ were the best, and at 1 090 ℃ were the worst. When the quenching temperature was the same, the test steel tempered at relatively low temperatures had higher tempering hardness, which could support the surface oxide layer, so its wear resistance was better than that tempered at relatively high temperatures. The recommended heat treatment process for 4Cr5Mo2V steel was 1 030 ℃×30 min oil quenching +560 ℃×2 h tempering for twice.

As-cast Mg-4Zn-4Y alloy was treated by homogenization annealing at different temperatures (440,460,480℃) for different holding times (4-24 h), and the effects of homogenization annealing on the microstructure and properties of the alloy were studied. The results show that there were α-Mg phase, W phase Mg₃Zn₃Y₂, LPSO phase Mg₁₂ZnY and yttrium-rich phase in the as-cast alloy. With increasing annealing temperature, most of the LPSO phase gradually dissolved into the matrix. With increasing annealing temperature and holding time, the content of yttrium-rich phase decreased, and the dendrite segregation was reduced. Compared with the as-cast alloy, the tensile strength of the alloy after homogenization annealing at 440℃ and 460℃ decreased slightly, and the percentage elongation after fracture changed slightly. The tensile strength and percentage elongation after fracture after homogenization annealing at 480℃ were relatively high, but the burning loss occurred. The best homogenization annealing of the alloy was 440℃×12 h.

SP-700 titanium alloy was treated by solid solution in β phase region at 1 000℃ for 15 min, and then was cooled to (α+β) phase region for solid solution at different temperatures (650-900℃) for different times (3-10 min) or was treated by single stage aging and or double stage aging including 280℃ low temperature pre-aging and the second aging at different temperatures (370-650℃) for different times (15, 90 min). The microstructure and properties of the alloy under different processes were studied. The results show that the volume fraction of α phase in the alloy after 850℃ solid solution increased with the solid solution time; when the solid solution time was 5 min, the alloy had good strong plastic matching. Under solid solution time of 5 min, the volume fraction of α phase decreased with increasing solid solution temperature; when the solid solution temperature was 650℃, the alloy had good strong-plastic matching. After β phase region solid solution and single/double stage aging, the alloy was basically composed of β grain, α phase and acicular martensite. After single stage aging at aging temperature of 650℃ for 90 min or double stage aging at aging temperature of 650℃ for 15 min, the alloy showed good strong-plastic matching.

N80 steel sheet was polished and then modified by fluorination with 1H,1H,2H, 2H-perfluorodecyltriethoxysilane, and the effect of fluorination modification on the corrosion resistance of the test steel in 3.5wt% NaCl solution and anti-scaling performance in simulated seawater was studied. The results show that after immersion in NaCl solution for 7 d, the surface corrosion of the fluorination modified specimen was the lightest, and the low frequency (0.01 Hz) impedance modulus was 450 Ω·cm², which was much larger than that of the unpolished and polished specimens. After seven-time rapid evaporation scaling tests, the scaling amount of the fluorination modified specimen was reduced by about 42.55% and 37.00% those of the unpolished and polished specimens, respectively. After 35-day of multi-field coupling scaling test, there was no obvious scaling phenomenon in the fluorination modified specimen, and the scaling amount was close to 0. Fluorination modification could improve the corrosion resistance and anti-scaling performance of N80 steel.

The weld toe area of a three-time repair welding joint of 30CrMnSiNi2A steel was treated by ultrasonic impact. The effects of the ultrasonic impact on the microstructure, mechanical properties and residual stress of the repair welding joint were studied by microstructure observation, tensile test, hardness test and residual stress test. The results show that the ultrasonic impact caused grain refinement and plastic deformation in the area about 100 μm from the surface of the repair welding joint. The influence of ultrasonic impact on the tensile properties of the welding joints was small because the thickness of ultrasonic impact affected layer was smaller than that of the welding parts. The microhardness of the repair welding joint surface increased significantly by ultrasonic impact, which was related to grain refinement and the increase of dislocation movement resistance on the surface of the repair welding joint. Ultrasonic impact could transform the harmful residual tensile stresses accumulated in multiple repair welding into beneficial compressive stresses.

The steel with a ferrite + pearlite microstructure was quenched at 910 ℃+tempered at different temperatures (500, 550, 600 ℃) to obtain the ultra-high strength grade casing drilling steel. The obtainal casing drilling steel was subjected to impact tests at different temperatures (-60-20 ℃). The effects of tempering and impact test temperatures on the impact toughness and fracture mechanism of the casing drilling steel were studied. The results show that as the tempering temperature increased, and the martensite in the casing drilling steel gradually disappeared, and the tempered sorbite structure was formed. Meanwhile, the impact energy consumed in room temperature impact increased, and the maximum impact load decreased. The impact fracture macromorphology of the steel tempered at different temperatures was both fiber zone and shear lip, and the fracture mechanism was ductile fracture. The ductile-brittle transition temperature of the casing drilling steel tempered at 550 ℃ was -33.64 ℃. As the impact test temperature decreased, the impact energy gradually decreased, the fracture macromorphology changed from a complete fiber region to a nearly complete radiation region, and the fracture micromorphology changed from complete dimple to a quasi-cleavage structure containing local dimple structures.

Taking composite steel pipe with TA2 industrial pure titanium lining and 20 steel coating as the research object, and BNi₂ amorphous alloy foil as the interlayer, the titanium/steel composite pipe was welded by transient liquid phase diffusion bonding at bonding temperatures of 1 130-1 200℃ under argon protection. The effect of bonding temperature on the microstructure and properties of titanium/steel composite pipe joints was investigated. The results show that the joints at different bonding temperatures were formed well without macroscopic defects such as holes and cracks. With increasing bonding temperature, the equiaxed microstructure of weld at the titanium side grew up, α→α'+β phase transition occurred, and the weld boundary became blurred gradually. The acicular ferrite and pearlite in the weld at the steel side became thicker, the black brittle phase gradually disappeared, and the diffusion distance of elements of interlayer and base material increased. The joints welded at different bonding temperatures all fractured in the weld at the titanium side. With increasing bonding temperature, the tensile strength of the joint increased first and then decreased. When the bonding temperature was 1 180℃, the tensile strength was the biggest of 460 MP, and the fracture form was ductile-brittle mixed fracture.

NiCuZn soft magnetic ferrite was prepared by solid state sintering with raw powder of different particle size prepared by changing the secondary ball milling time (1-6 h). The effect of the particle size on the microstructure and magnetic properties of the soft magnetic ferrite was studied. The results show that the powder particle size decreased with the extension of secondary ball milling time, and the size distribution gradually concentrated. The uniformity of grain size of soft magnetic ferrite prepared became better and then worse, and the grain boundary became clear and then blurred. With the decrease of the powder particle size, the initial permeability, saturation magnetic induction intensity, relative density and resistivity of the soft magnetic ferrite increased first and then decreased, and the power loss decreased first and then increased. When the secondary ball milling time was 3 h, the powder partide size was mainly between 2.5-3.5 μm, with average particle size of 3.237 μm. At this time, the grain boundary of the prepared soft magnetic ferrite was relatively clear, and the grain size was relatively uniform. The initial permeability and saturation magnetic induction intensity reached the maximum value of 1385 H·m^-1 and 360 mT, respectively, and the power loss reached the minimum value of 284 kW · m^-3.

Cu-Ni alloy powders were synthesized by ultrasonic assisted electrical discharge machining (EDM) method with copper and nickel metals as positive and negative electrodes, respectively. The effects of ultrasonic power (0, 500, 1 000, 1 500 W) on the crystal structure, micromorphology and particle size distribution of the alloy powder were investigated. The results show that the phases of Cu-Ni alloy powders synthesized by ultrasonic assisted EDM under different power conditions were all composed of Cu_0.81Ni_0.19, Ni, CuO, NiO and Fe₂O₃. The main crystal phase Cu_0.81Ni_0.19 had a face-centered cubic structure. With increasing ultrasonic power, the diffraction peak intensity of the Cu_0.81Ni_0.19 increased while the full width at half maximum became narrower, indicating the better crystallinity of the powder. Irregular particles with large size appeared in Cu-Ni alloy powders synthesized by the ultrasonic assisted method, but the size of spherical particles decreased and the distribution range of particle size became wider. With increasing ultrasonic power, the average particle size D₅₀ decreased.

Taking Al₂O₃ and TiC powders as raw materials, TiC-Al₂O₃ conductive ceramic composites were prepared by pressureless sintering technique. The effects of TiC content on the microstructure and properties of ceramic composites were investigated. The results show that TiC-Al₂O₃ conductive ceramic composites mainly consisted of Al₂O₃ phase and TiC phase. With increasing content of TiC, the relative density decreased, and the open porosity increased; when the TiC volume fraction was 30%, the ceramic composites had the maximum relative density of 95.5% and the minimum open porosity of 3.0%. The conductive phase TiC in ceramic composites was connected as a network structure; with increasing TiC content, the network structure formed by TiC became more complete,the hardness of ceramic composites increased first and then decreased, the resistivity and fracture toughness decreased, and the bending strength increased. When the TiC volume fraction was 45%, the bending strength was the highest and the conductivity was the lowest, which were 361 MPa, 6.95×10^-6 Ω·m, respectively.

A series of asymmetric stress-controlled uniaxial cyclic tests were performed on polyether-ether-ketone (PEEK) at room temperature, and the influence laws of stress level, loading history, stress rate and peak-stress holding time on the ratchetting behavior were studied. The results show that the PEEK exhibited obvious ratchetting behavior during the asymmetric stress cyclic loading, and the ratchetting strain consisted of the recoverable viscoelastic strain and the irrecoverable viscoplastic strain. Both the ratchetting strain and its rate increased with stress level. The ratchetting behavior of PEEK had an obvious loading history effect; the loading history under high mean stresses suppressed the ratchetting deformation in the subsequent cycle process under low mean stresses, and the loading history under low mean stresses had little effect on the ratchetting deformation in the subsequent cycle process under high mean stresses. The ratchetting behavior of PEEK showed obvious time-dependence; the lower the stress rate and the longer the peak-stress holding time, the larger the ratchetting strain.

The butt welding of 5083 aluminum alloy and 304 stainless steel was carried out by the cold metal transfer (CMT) twin fusion brazing process. Under the condition of ensuring good weld formation, the influence of welding heat input on the intermetallic compound (MC) layer thickness and tensile properties of the joint was studied and compared with that of the CMT single fusion brazing joint. The results show that the heat inputs of CMT twin and single fusion brazing joint weld to obtain good forming quality were 213.8-486.0, 379.6-590.6 J·mm^-1, respectively. IMC at the interface of CMT twin and single fusion brazing joints was FeAl₃ phase. With increasing heat input, the thickness of IMC layer of CMT twin or single fusion brazing joints increased, and the tensile strength decreased. The minimum thickness of IMC layer of CMT single fusion brazing joint was 9.59 μm, and at this time, the joint had the largest tensile strength of 76 MPa. The minimum thickness of IMC layer of CMT twin fusion brazing joint was 3.36 μm, and at this time, the joint had the largest tensile strength of 109 MPa.

0.2C-1.6Si-1.8Mn steel with initial martensite microstructures was subjected to austenitizing at different temperatures (840, 870, 910℃) and quenching-partitioning (Q&P) treatment. The effect of austenitizing temperature on the microstructure and tensile properties of the steel was studied. The results show that when the austenitizing temperature was in the two-phase region, the ferrite in the Q&P treated experimental steel was mainly banded, and the retained austenite was blocky and flaky. With the increase of austenitizing temperature, the content of ferrite and retained austenite decreased, and the content of martensite increased; accordingly, the yield strength and the tensile strength increased while the percentage elongation after fracture and the product of strength and elongation decreased. The higher percentage elongation after fracture of the Q&P treated experimental steel at austenitizing temperature of 840℃ was related to the higher content of the retained austenite with two forms of block and flake, which could effectively expand the transformation induced plasticity effect range.

Fe_50-xMn₃₀Cr₁₀Co₁₀(VC)_x (x=0, 1, 3, atomic fraction/%) high-entropy alloy coatings were prepared on Q235 steel plate surface by laser cladding technique. The effect of VC addition on the micromorphology, phase composition, hardness, wear resistance and corrosion resistance of the coating was studied. The results show that the high-entropy alloy coatings with three VC additions were well bonded with the substrate, and there were only a few defects such as holes in the coatings. The three coatings were all composed of solid solution phases with a face-centered cubic structure. With increasing VC addition, the structure of the high-entropy alloy coating was refined, and the microhardness increased. The addition of VC could improve both wear resistance and corrosion resistance of Fe₅₀Mn₃₀Cr₁₀Co₁₀ high-entropy alloy coating, and the more the VC was added, the better the wear resistance and corrosion resistance were.

Sn-(20-x)Bi-xIn (x=0,1,2,3,4,5, mass fraction/%) solder was prepared, and its melting and wetting properties were analyzed. Brazing experiments were conducted on copper substrate with Sn-(2-x)Bi-xIn solder, and the effect of indium content on the microstructure at the brazing interface was studied. The results show that with the increase of indium content, the melting point of the solder decreased. When the mass fraction of indium was 5%, almost no eutectic structure was formed in the solder. The wetting angle of the solder first decreased and then increased, and the wetting area first increased and then decreased with increasing indium content. When the mass fraction of indium was 4%, the wettability of the solder was the best. The thickness of intermetallic compound layer at the brazing interface increased, and the composition of the intermetallic compound changed from Cu₆Sn₅ to Cu₆Sn₅ and Cu₆(InSn)₅.

A modified combined high and low cycle fatigue life prediction model was established based on Manson-Halford model by studying the damage equivalence relationship between high cycle fatigue and low cycle fatigue, and introducing an influence factor to reflect the influence of the interaction between high cycle fatigue and low cycle fatigue loads. The modified model was verified by the test data of TC11 titanium alloy, LY12-CZ aluminum alloy, 45 steel and GH4033 nickel-base alloy. The results show that the fatigue life prediction results of TC11 titanium alloy, LY12-CZ aluminum alloy and GH4033 nickel-base alloy by using the modified model were within the range of two times of error. About 78% of the predicted fatigue life of 45 steel was in the range of two times of error. The modified model had high prediction accuracy and was suitable for the prediction of high and low cycle composite fatigue life.

304L stainless steels with two different grain size were fabricated by cold rolling and annealing at 900℃ and 700℃, respectively. The effect of grain size on room-temperature and high-temperature tensile properties of the steels was studied. The results show that the annealing treatment made the cold-rolled elongated grains recrystallize to form equiaxed grains. When the annealing temperature was 900℃ and 700℃, the average grain size was 63 μm and 3 μm, respectively. During tension at 25℃ and 200℃, the yield strength of the test steel with fine grains was higher than that of the test steel with coarse grains, but the percentage elongation after fracture was lower than that of the test steel with coarse grains. When the tensile test temperature increased to 800℃, the tensile fracture of the two grain size test steels both exhibited a transgranular+intergranular mixed fracture mode, indicating the grain boundary did not play a significant strengthening role; therefore, the strength and percentage elongation after fracture of the two grain size test steels stretched at 800℃ were basically the same.

Nanobeam precursor was prepared by solvothermal reaction at 200 ℃ with zinc acetate, manganese acetate and ammonium bicarbonate as raw materials and seignette salt as structure guide agent. The optimal addition amount of seignette salt and solvothermal reaction time were determined according to the shape of the precursor. The ZnMn₂O₄ nanobeams for cathode of lithium ion batteries were prepared by calcining the precursors at 250, 350 ℃ for 2 h. The microstructure and electrochemical performance of the ZnMn₂O₄ nanobeams were stdied. The results show that one-dimensional nanobeams with intact structure could be obtained when the solvothermal time was 12 h and the seignette salt addition amount was 1 mmol. The ZnMn₂O₄ nanobeams could be obtained at the two calcining temperatures, but the ZnMn₂O₄ nanobeams obtained at 350 ℃ showed better electrochemical performance; the specific capacity of ZnMn₂O₄ nanobeams could still be maintained at 892 mA·h·g^-1 after 60 cycles at current density of 100 mA·g^-1. Under the high current density of 2 A·g^-1, the specific capacity could still reach 416.2 mA·h·g^-1.

As-cast Ti₂₈Co₁₄Ni_37.12Zr_20.88 high entropy alloy was tempered at different temperatures ( 673,723 K). The effects of tempering temperature on the microstructure and mechanical properties of the high entropy alloy were studied. The results show that the microstructures of the as-cast, 673 K tempered and 723 K tempered alloy were composed of a TiNi matrix phase of a body-centered cubic structure and a small amount of a face centered cubic structure Ti₂Ni second phase. With the increase of tempering temperature, the grains of TiNi phase and Ti₂Ni phase were refined. After tempering heat treatment, the elastic limit and yield strength of the as-cast alloy increased. The compressive strength of the 673 K tempered alloy was lower than that of the as-cast alloy, but when the tempering temperature increased to 723 K, the compressive strength increased and was higher than that of the as-cast alloy. The fracture mechanism of the as-cast high entropy alloy was mainly cleavage fracture, supplemented by intergranular fracture and ductile fracture. The fracture mechanism of the 673 K tempered and 723 K tempered high entropy alloy was mainly cleavage fracture, supplemented by intergranular fracture.

SiO₂ filled hydrocarbon resin copper clad laminate was prepared by impregnation and vacuum hot pressing technology with polybutadiene as resin matrix, glass fiber cloth as reinforcement and SiO₂ as filler, and the effects of SiO₂ particle morphology (spherical shape and irregular shape) and particle size (2-20 μm) on the dielectric properties, bending strength, peeling strength and water absorption of copper clad laminates were studied. The results show that with the same particle size, compared with the irregular SiO₂ filled hydrocarbon resin copper clad laminate, the spherical SiO₂ filled hydrocarbon resin copper clad laminate had relatively low dielectric constant, dielectric loss and water absorption, relatively high bending strength and peeling strength, and relatively good comprehensive performance. With increasing particle size of SiO₂, the dielectric constant, dielectric loss, bending strength and water absorption of the spherical and irregular SiO₂ filled hydrocarbon resin copper clad laminate decreased, while the peeling strength increased.

CoCrFeNiW_x(x=0.2, 0.5, mole fraction/%) high entropy alloy powder was prepared by mechanical alloying method. The powder was mixed with WC powder as a binder (adding mass fraction was 6%, 10%, 14%, respectively), and then WC cemented carbides were obtained by spark plasma sintering. The effect of the high entropy alloy binder on the microstructure and mechanical properties of the cemented carbide was studied. The results show that the CoCrFeNiW_x high entropy alloy binder had a face-centered cubic and body-centered cubic dual-phase structure and could refine grains in WC cemented carbides. With the increase of high entropy alloy binder content, the Vickers hardness of the WC cemented carbide decreased, and the fracture toughness and bending strength had a general increase trend. The WC cemented carbide prepared by adding 10wt% CoCrFeNiW_0.2 high entropy alloy binder had the best comprehensive performance, with Vickers hardness of 1 785 HV, fracture toughness of 10.6 MPa·m^1/2, and bending strength of 1 373 MPa.

Friction stir welding of 7N01 aluminum alloy was carried out under different press amounts (0.3, 0.7, 1.0 mm). The effects of press amounts on the cross-sectional morphology, tensile properties, anti-tear properties, and fatigue properties of the joint were studied. The results show that the press amount had little effect on the tensile properties of the 7N01 aluminum alloy friction stir welding joint. When the press amount was 0.7, 1.0 mm, respectively, the crack initiation energy, crack propagation energy, and tear strength of the joint were similar. When the press amount was 0.3 mm, the crack initiation energy, crack propagation energy, and tear strength of the weld area of the joint were significantly reduced. The fatigue strength of the welding joint increased with the increase of the press amount. The fatigue properties and crack propagation resistance of the welding joint were the best when the press amount was 1.0 mm.

Ti-46Al-8Nb (atomic fraction/%) alloy was directionally solidified by using BaZrO₃/Al₂O₃ composite mold shell with Bridgman furnace. The interface erosion layer morphology, microstructure and phase composition of the alloy, and the effect of the crystal selector angle on the crystal selection efficiency and the alloy lamellar orientation were studied. The results show that after directional solidification, a 10 μm thick erosion layer existed at the bottom of the alloy. With increasing height, the oxygen content in the alloy and the thickness of the erosion layer increased. The alloy had a full lamellar structure composed of γ (TiAl) and α₂ (Ti₃Al) phases, and no inclusions existed. Within 30°-60°, the smaller the crystal selector angle was, the higher the crystal selection efficiency was. The crystal selector angle had little effect on the angle between the alloy lamellar orientation and growth direction.

Niobium containing dual phase steel hot-rolled under the same process parameters was cooled to 610 ℃ by primary water cooling at a cooling rate of 60 ℃·s^-1 or to 461, 434, 410 ℃ by two-stage water cooling at different cooling rates and coiled. The effects of the coiling temperature and cooling rate on the microstructure and tensile properties of the hot-rolled dual phase steel were analyzed. The results show that the microstructures of the hot-rolled dual phase steel under the four processes were all mainly composed of ferrite and martensite, and bainite appeared at the coiling temperature of 461 ℃ and below. With the decrease of coiling temperature, the content of martensite decreased, and the bainite presented dispersed granular, aggregated granular and lath shape successively. The yield strength of the hot-rolled dual phase steel increased, the tensile strength first decreased and then increased, the yield ratio increased, and the precentage elongation after fracture first increased and then decreased. When two-stage water cooling at primary and secondary cooling rates of 53,79 ℃·s^-1 to 461 ℃ and coiling, the tensile properties of the hot-rolled dual phase steel were the best, with the average yield strength, average tensile strength, and average precentage elongation after fracture of 459 MPa, 591 MPa, and 35.63%, respectively.

Isothermal compression tests were conducted on electron beam cladding solidified Inconel 718 alloy (EBLS 718 alloy) and electron beam refining Inconel 718 alloy (EBS 718 alloy). The deformation temperatures were 1 010, 1 050, 1 100, 1 140 ℃, and the strain rates were 0.001,0.01,0.1,1 s^-1. The thermal deformation rheological behaviors of the two alloys were compared and studied. Based on the Arrhenius constitutive equation, the constitutive equations of the two alloys were established. The results show that the rheological behavior of the two alloys under different deformation temperatures and strain rates was similar; the flow stress increased with increasing strain rate, and decreased with increasing deformation temperature. Due to the layered interface, the EBLS 718 alloy exibited yield decrease phenomenon at a lower temperature during hot compression deformation, lower deformation activation energy, and more obvious dynamic softening effect. The main deformation mechanism of the two alloys was mainly high temperature climbing mechanism caused by lattice self diffusion.

A high-temperature fretting wear tester was used to conduct tangential fretting wear tests of Zr-4 alloy tubes, and the effects of test temperature (25,100,200,325℃) on fretting wear behaviors under different operating conditions (complete slip region and partial slip region) were studied by changing normal load. The results show that the friction coefficient in the complete slip region was higher than that in the partial slip region at the same test temperature, and the friction coefficient at 200, 325℃ under different operating conditions reached stability earlier. In the complete slip region, the wear mechanism of the alloy included abrasive wear, oxidation wear and delamination; the increase of temperature had great influence on fretting wear degree of the alloy, and the fretting wear degree reached the maximum at 325℃. In the partial slip region, the wear mechanism included delamination, adhesive wear and oxidation wear, and the fretting wear degree was little affected by the increase of test temperature. At the same temperature, the fretting wear in the partial slip region was much lower than that in the complete slip region. The increase of test temperature had obvious effect on fretting wear amount in the complete slip region, but had little effect on that in the partial slip region.

The current-carrying friction and wear tests of carbon ceramic composite for brake disc were carried out by the pin-disk friction and wear testing machine, and the friction and wear properties of carbon ceramic composite under different friction conditions were studied. The results show that in rainwater environment without current-carrying, with rainwater flow rate increasing from 0 to 1 mL·min^-1, the surface roughness of carbon ceramic composite decreased significantly, while the friction coefficient and wear rate decreased slightly; the wear mechanism included spalling and slight oxidation wear. Under the current-carrying condition without rainwater, with current intensity increasing from 0 to 100 A, the surface roughness and friction coefficient decreased significantly, and the wear rate increased obviously; the wear mechanism included spalling, abrasive wear, adhesive wear and arc ablation. Compared with those affected by the single factor, the surface roughness and friction coefficient decreased significantly under the combined action of current carrying and rainwater, but the law of the wear rate increasing with the rainwater flow or the current intensity was not obvious; the wear mechanism was spalling, oxidation wear, abrasive wear and adhesive wear.

AlN and BN were modified with silane coupling agent KH570 under anhydrous conditions, and then were used as thermal conductive fillers added into glass fiber reinforced styrene-butadiene resin composites. The effect of different thermal conductive fillers on the water absorption, thermal conductivity, dielectric properties and mechanical properties of the composite was studied. The results show that filling the two thermal conductive fillers could improve the water absorption of the composite; comparing with the unmodified filler, the filling of the modified filler had a small increase in water absorption of the composite. With the increase of modified AlN content, the dielectric constant and dielectric loss of the composite increased significantly, indicating the dielectric properties decreased, and the flexural strength increased first and then decreased. With the increase of modified BN content, the dielectric constant of the composite increased, the dielectric loss decreased, and the flexural strength increased. The two modified thermal conductive fillers could improve the thermal conductivity of the composite. Compared with single component filling, modified AlN and modified BN hybrid filling had a stronger effect on improving the thermal conductivity of the composite.

Tungsten inert gas wire arc additive manufacturing was carried out with the GH4169 superalloy welding wire. The prediction model of the relationship between welding current, welding speed, wire feeding speed and the size of single pass multi-layer welding bead layer width and layer height was established by the quadratic regression general rotation combination scheme, and the calculation was verified by test. The results show that the maximum relative errors of the prediction model of the layer width and the layer height of single pass multi-layer welding bead were 5.22% and 5.82%, respectively, indicating that the established prediction model had high reliability. The effect of welding speed, welding current and wire feeding speed on the forming size of single pass multi-layer welding bead was coupled with each other. The biggest factor affecting the layer width of single pass multi-layer welding bead was the welding current, and the biggest factor affecting the layer height was the wire feeding speed.

The forged pure tin plate with purity of 99.99% was treated by equal channel angular pressing (ECAP) for different passes (0-20 passes) at room temperature. The effect of ECAP pass on the microstructure and mechanical properties of the pure tin was studied. The results show that under the severe shear of ECAP, twinning and twin-induced recrystallization occurred in pure tin grains, and the grains were significantly refined. After ECAP for more than 12 passes, the grain refinement effect was weakened. With increasing ECAP pass, the texture strength and maximum orientation density of the pure tin decreased, while the hardness, strength and percentage elongation after fracture increased. Compared with those of the forged pure tin, the hardness, yield strength, tensile strength and percentage elongation after fracture after 20 passes of ECAP increased by 9.09%, 5.14%, 32.08% and 144.19%, respectively. The main strengthening mechanism of the pure tin was work hardening with ECAP pass of less than 8, and was fine grain strengthening with ECAP pass of more than 8.

A finite element model of 4.6 mm thick armor steel target plate shot by ordinary steel core bullet was established, and the residual stresses distributed along the plate thickness direction, which were measured by experiments, were assigned to the finite element model. The influence of the initial residual stress of the target plate on its anti-ballistic performance was studied, and the simulation results were verified by the test results. The results show that the simulation results of the back bulge height and crater depth of the target plate with initial residual stresses were consistent with the test results, and the relative errors were only 2.0% and 4.8%, respectively, indicating that the model was accurate. Comparing with those without initial residual stresses, the back bulge height and crater depth of the target plate with the initial residual compressive stress were reduced, indicating the anti-ballistic performance of the steel plate was improved. With the increase of applied residual compressive stresses, the anti-ballistic performance of the target plate showed a slight increase trend, but the increase was very small.

A low-cost Fe-Cr-Ni medium-entropy alloy was developed. The corrosion resistance of the medium-entropy alloy in a 0.1 mol·L^-1 H₂SO₄ solution was studied by comparing with that of 316L stainless steel, and the protective ability of the surface passive film was analyzed. The results show that comparing with 316L stainless steel, the test alloy had a higher free-corrosion potential and a smaller free-corrosion current density, indicating the stronger corrosion resistance, slower corrosion rates and better corrosion resistance. Comparing with those of 316L stainless steel, the content of chromium and nickel in the passive film on surface of the test alloy was higher, and the content of iron and manganese was lower; the charge transfer resistance was 8.1 times that of 316L stainless steel. This showed that a more protective passive film was formed on surface of the alloy. The test alloy had a stable single-phase face-centered cubic solid solution structure, and the degree of element segregation was low, which improved the passivation ability and reduced the corrosion sensitivity of the alloy, thus ensuring the stability and protection ability of the passive film.