Magnesium alloys are the lightest structural alloys developed so far and have a great potential for lightweight applications, ranging from portable electronic devices to automobile parts. Comparing to Mg alloys containing no rare earth (RE), Mg-RE alloys attracted more and more attentions due to the higher strengths at both room temperature and elevated temperature. Strengthening methods for Mg alloys with high RE contents and low RE contents were introduced respectively in this paper. For Mg alloys with high RE contents, precipitates of β' lying in the triangular prismatic plates can impede dislocation slip effectively to enhance the strength of the alloy. For Mg alloys with low RE contents, the microstructure containing nano grains in the surface layer and twinning in the center can be obtained by surface mechanical attrition treatment. Thus the Mg alloy can be strengthened by both refinement strengthening of nano grains and twinning strengthening of RE segregated twin boundaries.

The paper presents the domestic and overseas current status of the steel applied to aircraft landing gear in combination of the design concept and requirements for aircraft landing gear. The application features and concept of the steel used for landing gear are summarized and the domestic and overseas status are compared. For the moment, the low-alloy ultra-high strength steel and high-alloy ultra-high strength steel are all being used in the material system for aircraft landing gear steel, and the complete technical system for its anti-fatigue manufacturing is built. At present, China's development and application of high strength steel applied to aircraft landing gear is at the world advanced level. At last, the prospect for future development is analyzed.

The AlSi10Mg powder was prepared by supersonic gas atomization. After classified, the powder was fabricated into block by selective laser melting (SLM). The microstructure, phase, and evolutions of powder and block were investigated by optical microscope, scanning electron microscope and X-Ray Diffraction. The tensile properties of SLM block were tested by tensile experiments at room temperature. The results show that the size distribution of AlSi10Mg powder after classified can meet the requirements of SLM technology. The powder always is spherical and spherical-like. Meanwhile, the microstructure of powders is fine and uniform, which contain α(Al) matrix and (α+Si) eutectic. In addition, the melt pool boundaries of SLM block are legible. The microstructure is also uniform and densified, the relative density approaches to 99.5%. On the other hand, only α(Al) and few Silicon phase are detected in this condition, due to the most alloying elements are dissolved in α(Al) matrix. At room temperature, the ultimate tensile strength of SLM block reaches up to 442 MPa.

The harsh space environment and its influence on the performance of space tribological materials are reviewed. The effects of the harsh space environment on the friction and wear mechanisms of friction materials, anti-wear materials and anti-friction materials are analyzed respectively. Space friction materials which are often used in space docking system and space manipulator should have stable friction torque and excellent adhesive wear resistance. Space anti-wear materials are mainly used in the space bearings, gears and seal parts. For example, The metal elements (e.g. Ce, Cr, Mn, Mo, Nb, W) and solid lubricants are often added for Fe-Al intermetallics to restrain creep at high temperature; the wear resistances of Ti and its alloys are often improved by surface modification; anti-wear coating which has a proper associativity with the matrix can improve the wear resistance of the materials. Space anti-friction materials mainly refer to lubricants and self-lubricating materials which can reduce friction coefficient of the materials, such as soft metals, polymer materials, some oxides, fluorides and sulfides. With the development of aerospace science and technology, it is highly demanded that the novel tribological materials with high performance should be developed for space applications, and the database of tribological materials should be built, in order to meet the international challenge of development of space technology.

Surface integrity state after machining has an important effect on the service life of metal parts and components. The effects of four kinds of surface integration processing methods on the high-temperature fatigue properties of FGH95 alloy were investigated. These four surface processing methods were AR (grinding), GCSSP (grinding and cast steel shot peening), GCSP (grinding and ceramic shot peening) and GDSP (grinding and double shot peening). The surface roughness, residual stress distribution and micro-hardness were characterized by roughness tester, X-ray diffraction (XRD) stress tester and micro-hardness tester. The rotating-bending fatigue life with notched specimens (stress concentration factor, K_t = 1.7) was investigated. The results indicate that the fatigue life of specimens increased largely by GCSSP, GCSP and GDSP compared with AR specimens respectively. Furthermore, GDSP process can obtain the best surface residual stress field distribution, gradient distribution of micro-hardness, surface roughness and improvement of the high-temperature fatigue property.

With the development of advanced aviation engines in the direction of high thrust-to-weight ratio and lightweight, a series of lightweight aviation materials such as titanium alloys, nickel-based high-temperature alloys, and ceramic-based composite materials have emerged and been widely used for the key components in the aerospace field, and have also become the main production materials for aero-engine blades. However, due to the stress concentration sensitivity of carbide and the anisotropy and brittle mechanism of composite materials, the fatigue failure problem is gradually highlighted. Existing studies show that the fatigue resistance performance of aero-engine blades has important relationship with its processing process, which in turn affects the service performance and service life of the equipment. Grinding, as the final material removal process for aero-engine blades, directly determines the final surface integrity and fatigue resistance of the blades while obtaining precise profiles. In order to understand the characteristics of blades processed by new lightweight aviation materials, and provide guidance for the processing of aero-engine blades for optimization of fatigue performance, the application of typical aero-engine blade materials and the research status of anti-fatigue grinding technology are summarized. Firstly, the characteristics of typical lightweight and high-strength aeronautical materials and their application in the production of aero-engine blades are briefly described. Secondly, the method of high surface integrity grinding and the key technology of anti-fatigue processing of aero-engine blades are analyzed. Finally, the research on anti-fatigue grinding of aero-engine blades is prospected.

Additive manufacturing technology (AM) is a new type of manufacturing technology based on the discrete-stacking principle and processing component with computer model data. Selective laser melting (SLM) is an important technology in the field of additive manufacturing. With its integrated manufacturing characteristics and significant advantages in the field of complex structural parts manufacturing, it has become a key development technology and frontier direction in the field of aerospace manufacturing. This article reviews the material system and application fields of SLM technology, and mainly analyzes the latest process research of SLM technology and typical applications in the aerospace field. It focuses on the research progress and results of SLM iron-based alloys, nickel-based alloys, titanium alloys and aluminum alloys. While SLM technology is widely used in various fields, there are also many problems and shortcomings, such as many internal defects of forming materials, cracks and deformations of high-performance materials, lack of standard systems, and low compatibility of powder materials. Constraints require further in-depth work in these areas.

The influence of different grades of prior particle boundary (PPB) in PM FGH96 superalloy during high-cycle fatigue test at 550 ℃ was investigated by the in-situ fatigue test in SEM. The results show that the PPB in P/M FGH96 superalloys by plasma rotating electrode process (PREP) + hot isostatic press (HIP) is constituted of large size γ' and carbide. There are no significant effect on the initiation and propagation of high cycle fatigue crack in different grades of PPB. Crack initiation is initiated in the grain interior, and the propagation is transgranular or intergranular, which is influenced by the angle between the grain boundary and the stress axis. In the fast crack growth zone and the transient zone, the fracture characteristics of serious grade PPB FGH96 superalloy are transgranular and along PPB globular surfaces.

The change of fatigue life and microstructure of 2124-T851 thick plate after cold expanded with different deformation was studied by fatigue test, TEM, SEM and X-ray diffraction apparatus. The results show that the fatigue life increases with the increase of expanded deformation until the maximum value is reached, and then decreased rapidly with the increase of expanded deformation. At 0.4 mm expanded deformation, fatigue life reach peak value, which is 12.66 times of the non-cold-worked specimens. The microstructure research results show that the residual compressive stress and dislocation cell structure form around the cold-worked holes during the cold expansion, and increase quickly with the expanded deformation. The strengthened layer retarded the fatigue crack growth rate. The appropriate cold expanded deformation can improve the surface roughness of hole, and retard the initiation of fatigue crack, consequently improving the whole fatigue life.

Structural stabilities, mechanical properties and electronic structures of Al₂Cu, Al₂CuMg and MgZn₂ intermetallics in Al-Zn-Mg-Cu aluminum alloys were determined from the first-principle calculations by VASP based on the density functional theory. The results show that the cohesive energy (E_coh) decreases in the order MgZn₂ > Al₂CuMg > Al₂Cu, whereas the formation enthalpy (ΔH) decreases in the order MgZn₂ > Al₂Cu > Al₂CuMg. Al₂Cu can act as a strengthening phase for its ductile and high Young's modulus. The Al₂CuMg phase exhibits elastic anisotropy and may act as a crack initiation point. MgZn₂ has good plasticity and low melting point, which is the main strengthening phase in the Al-Zn-Mg-Cu aluminum alloys. Metallic bonding mode coexists with a fractional ionic interaction in Al₂Cu, Al₂CuMg and MgZn₂, and that improves the structural stability. In order to improve the alloys' performance further, the generation of MgZn₂ phase should be promoted by increasing Zn content while Mg and Cu contents are decreased properly.

Based on the experiments of isothermal forging wedge-shaped samples, Deform-3D numerical simulation software was used to confirm the strain distribution in the wedge-shaped samples. The effect of deforming temperature and strain on abnormal grain growth(AGG) in extruded FGH96 superalloy was examined. It is found that when the forging speed is 0.04 mm/s, the critical AGG occurring temperature is 1100℃, and the critical strain is 2%.AGG does not occur within 1000-1070℃, but still shows the feature of 'critical strain', and the region with strain of 5%-10% has the largest average grain size.AGG can be avoided and the uniform fine grains can be gained when the strain is not less than 15%.

The influence of Cu content on microstructure and properties of 2219 aluminum alloy was investigated by using tensile tests, welding tests, electrochemical impedance spectroscopy (EIS), cyclic anodic polarization curves (Tafel) combined with optical microscopy (OM) and scanning electron microscopy analysis (SEM). The results indicate that the residual crystal phase in the matrix of 2219 aluminum alloy is reduced with the decrease of Cu content which contributed to effectively suppress the precipitation of Al₂Cu coarse phase during the welding process. Furthermore, with the decrease of Cu content, elongation of the alloy is significantly increased, while the tensile strength and yield strength is slightly decreased. At the same time, Al₂Cu phase formed in the matrix induces localized corrosion which causes the deterioration of corrosion resistance in the alloy, while the corrosion tendency of the alloy can be reduced by the decrease of Cu content and the corrosion resistance of the alloy is improved.

The corrosion of aluminum alloy in marine atmospheric environment was an essential electrochemical corrosion under thin electrolyte film, which was different from the corrosion in bulk solution, the corrosion rate was related to the thickness and composition of thin electrolyte film. The relationship among film thickness, relative humidity and salt deposit on aluminum alloy surface was established and verified by experiment. The electrochemical properties of 7B04 Al-alloy under thin electrolyte film with different thickness and different NaCl concentration were studied. The results indicate that the free-corrosion potential of 7B04 Al-alloy under thin electrolyte film is easier to reach steady state than that in bulk solution, both free-corrosion potential and corrosion rate are higher under thin electrolyte film. With the decrease of film thickness, the cathodic polarization current density of 7B04 Al-alloy increases, and the anode reaction is suppressed. With the increase of NaCl concentration in thin electrolyte film, the free-corrosion potential of 7B04 Al-alloy decreases, and the corrosion rate increases, but the polarization of the anode and cathode have little effect on the change of NaCl concentration. The free-corrosion potential of 7B04 Al-alloy is no longer changed when the mass fraction of NaCl reaches 5%.

The morphologies, surface energies and surface chemical properties of the domestic T700 grade carbon fiber and the T700S carbon fiber were characterized by using scanning electronic microscopy (SEM), inverse gas chromatography (IGC) and X-ray photoelectron spectroscopy (XPS) respectively.The mechanical properties of the two carbon fibers/QY9611 composites were also discussed. The results indicate that the surface properties of carbon fibers have an important influence on the interfacial properties of composites. The interfacial properties of domestic T700 grade carbon fibers/QY9611 composite at room temperature/dry conditions are superior to T700S/QY9611 composite. The toughness of domestic T700 grade carbon fibers/QY9611composite is outstanding as well. The value of CAI has reached the level of foreign advanced composite IM7/5250-4. After hydrothermal treatment, the interfacial strength of domestic T700 grade carbon fibers/QY9611 composite is equal to that of T700S/QY9611 composite. It shows that domestic T700 grade carbon fibers/QY9611 composite has good hydrothermal-resistant properties.

Through-thickness microstructure and mechanical property of AA 7055-T7751 aluminum alloy plate were investigated by using electron backscattered diffraction (EBSD), transmission electron microscope (TEM) and small angle X-ray scattering(SAXS). The results indicate an inhomogeneous distribution of microstructure through the thickness. The degree of recrystallization decreases gradually from 69% to 19.1%, as deepening from the surface to the center of the plate. The size of subgrains decreases from 10 μm at the surface to around 2 μm at the center. Strong texture of rolling type is observed near the center but the intensity decreases gradually as nearing the surface and the shear texture becomes the dominant. High density of plate-like η' phases are observed in the alloy, indicating the sufficient precipitation. η' precipitates of this condition are around 3.7 nm in radius, 1-3 nm in thickness and are found coherent with the Al matrix with a coherent strain of 0.0133, showing a strong strengthening effect. The heterogeneity in grain scale does not influence the distribution and the morphology of precipitates. The yield strength (L direction) varies linearly along the thickness direction of the plate, fitting an equation of σ_y=-38.7S+604.8 (0≤S≤1). The variation of yield strength is related to the heterogeneity of grain structure.

As a non-conduct and whole field measurement method, 3D DIC (3D digital image correlation) is widely used in mechanical properties test of many types of materials in varies fields. Compared with other optical measurement methods, it has advantages as automation, simple optical path, strong universality and anti-interference and so on. But it has some problems in the process of application, i.e. the measurement accuracy is uncertain, the high temperature test condition seriously affects the experimental results, and the measurable area of large curvature specimen is limited. This paper gives a general introduction to the application of 3D DIC in the conventional mechanical property test of different types of materials, and verifies its accuracy by comparing with the traditional extensometer measurement results and the finite element simulation results. It focuses on some latest technological progress, such as the high-temperature speckle preparation and multi-camera DIC, as the application of 3D DIC in the high temperature and large deformation measurement is mostly studied. Moreover, it is pointed out that 3D DIC should be further studied for the influence of speckle on measurement precision, the effect of environmental factors, the measurement of micro strain scale and the application in fields of military and biomedical materials.

In order to improve the fatigue performance of TC17 central hole specimen, the hole wall surface integrity was characterized by scanning electron microscopy (SEM), roughness meter, X-ray diffraction, and the influence of hole cold expansion(HCE) parameter on the fatigue performance of the hole specimens was investigated. The results show that the minimum fatigue life (14718 cycle) of the HCE specimens with an expansion value of 0.18 mm is higher than the original specimen (13965 cycle). Compared to the specimens with the expansion values of 0.28 mm and 0.38 mm, the fatigue life dispersion is less, no obvious stress concentration phenomenon is found, and it has the best fatigue performance than the other two. The surface roughness value of hole wall is the lowest after the HCE with 0.18 mm, the inner hole wall forms a certain depth of strengthened layer, the residual compressive stress produced in the hole side effectively suppresses the produce of fatigue cracks in the inner hole wall, so the fatigue performance of hole structure is improved.

To improve the fatigue resistance of the bolt connecting hole, the effect of double cold expansion (DCE) of the hole on the fatigue life of TB6 titanium alloy was investigated. The fatigue fracture, surface roughness, residual stress, hardness and microstructure of the hole wall were characterized by scanning electron microscopy (SEM), roughmeter, X-ray diffraction (XRD), microhardness tester and optical microscopy. The mechanism of DCE on the fatigue life of the hole was also investigated. The results show that the mean value of the fatigue life of DCE specimen is much higher than that of the interference fit specimen. The surface integrity of the hole wall is improved after DCE. The roughness decreases remarkably. The deep surface-strengthen-layer with high hardness and deep residual compressive stress field are formed around the hole through severe plastic deformation of the microstructure of the hole wall. It is considered that the improvement of surface integrity plays an important role on the enhancement of fretting fatigue life.

In order to break through the technical bottleneck of traditional Mo/8YSZ double- layer thermal barrier coating which is easy to peel off at high temperature, the influence of the thickness of matrix, bonding layer, transition layer and ceramic layer on the residual stress of Mo/8YSZ functional gradient thermal barrier coating were studied. The numerical model of plasma spraying Mo/8YSZ functional gradient thermal barrier coating was established by using ANSYS finite element software. In the model, the variation of material thermal and physical parameters with temperature was considered, and the influence of different substrate, bonding layer, transition layer and ceramic layer thicknesses on the residual stress of functional gradient thermal barrier coating was analyzed. The results show that the maximum radial residual tensile stress and maximum radial residual compressive stress decrease with the increase of substrate thickness. With the increase of the thickness of bond layer, transition layer and ceramic layer, the maximum radial residual tensile stress increases and the maximum radial residual compressive stress decreases. Residual compressive stress is the main form of axial residual stress, with the increase of substrate thickness, maximum axial residual compressive stress of coating decreases, and with the increase of bonding layer or transition layer thickness, the maximum axial residual compressive stress increases, however, the change of ceramic layer thickness does not obviously effect the maximum axial residual compressive stress. The effect of changing the thickness of adhesive layer on the interface residual compressive stress is more obvious. The influence of the thickness of the matrix on the interface residual stress between the matrix and coating is within a certain range. When the substrate thickness increases to 12 mm, with the increase of the substrate thickness, the variation difference of the radial residual stress between the substrate and coating interface decreases. With the increase of the substrate thickness, the transition point and stress transition point of the stress form gradually transfer to the upper part of the boundary between the substrate and coating. With the increase of the thickness of the bonding layer, transition layer or ceramic layer, the transition point and stress transition point of the stress form gradually transfer to the lower part of the central area of the interface between the substrate and coating. By designing the functional gradient thermal barrier coating and adjusting the structural parameters of the thermal barrier coating system reasonably, the residual stress and stress mutation of the spraying component can be further reduced and the bonding strength between the substrate and coating can be improved.

Nickel-based superalloys, titanium alloys, stainless steel and other metal materials are widely used in high-end equipment manufacturing, especially in the field of national defense and military industry. Grinding process is an important method to machine these difficult-to-cut metal materials. However, the thermomechanical coupling effect in grinding process has a significant effect on surface integrity, while the surface integrity contributes to the service performance of parts. In this paper, the formation mechanism, contributing factors, prediction and control of the core elements (such as surface roughness, residual stress, micro-hardness and microstructure, etc.) of surface integrity were comprehensively summarized. The development trend of surface integrity control technology is also prospected.

Thermal barrier coating (TBC) is a kind of thermal insulation and protective ceramic material, which can effectively improve the working temperature and service life of aero-engine. It has important economic value and strategic position in this field. With the further improvement of thrust-to-weight ratio, the traditional YSZ coating no longer can meet the technical requirements of the new generation engine. In recent years, scholars both at home and abroad have shown that rare earth doping can improve the performance of TBCs to a certain extent. Therefore, rare earth doping modification has become the focus of the development of new high-performance TBCs. In this paper, the applications of rare earth doping in high-performance TBCs are summarized, with emphasis on the effects of rare earth doping on the mechanical, thermal-physical and corrosion resistance of TBCs to molten CMAS. The problem of performance deterioration of TBCs when rare earth is over doped and the deficiency in rare earth selection standard is discussed. Moreover, it is considered that the selection basis of rare earth doping amount and type will be the research focus of TBC materials in the next generation. How to further improves the performance of TBCs is the future development direction of rare earth doped TBCs.

The basic features of A-100 steel, such as relationship between cogging process and mechanical properties, relationship among the forging process, grain size and mechanical properties, secondary hardening, and fatigue properties were discussed. The high-temperature homogenization and high deformation at first step technique were developed on the foundation of multiple upsetting and stretching, high forging ratio technique used for 300M steel, and became the technique foundation of cogging process in A-100 steel. The fracture toughness of A-100 steel was tended to be influenced by hot working process. The grain size grew heavily, and mixed grain structure was appeared after heating at 1140℃ and above with deformation amount below 20%, the fracture toughness was also decreased. The secondary hardening performance of A-100 steel was changed after the deformation at low temperature. The tensile strength peak temperature was changed to 468℃, the tensile strength was decreased slowly when over aging. A-100 steel was cyclic hardened, and its fatigue crack growth properties were better than 300M steel. The high cycle fatigue property was heavily deteriorated when tested in 3.5%NaCl solution.

Hardness gradient, residual stress gradient and the organization structure of surface super-hardened M50NiL steel roller and M50 steel roller were studied, the rolling contact fatigue life was measured, and the failure process was analyzed and compared by using surface profiler, Vickers hardness tester, X ray residual stress determinator, optical microscope, scanning electron microscope (SEM), rolling contact fatigue test machine and other equipment. The fatigue failure mechanism of surface super-hardened M50NiL steel was revealed. The results show that the fatigue failure mechanism of surface super-hardened M50Nil steel returns to the Hertz theory and shows typical contact fatigue characteristics. The high surface hardness, residual compressive stress and a good organization structure can completely inhibit the initiation of surface cracks; therefore, the failure mechanism is returned to the Hertz theory.

Through turning and rotary bending fatigue test, the effect of turning feed on GH4169 superalloy surface integrity, and the effect of surface integrity on fatigue life were studied. The results show that the surface roughness R_a decreases from 1.497 μm to 0.431 μm when the turning feed decreases from 0.2 mm/r to 0.02 mm/r. The surface residual stresses are changed from tensile stress to compressive stress. The depth of plastic deformation layer decreases from 8 μm to 2 μm. The surface stress concentration factor has the most significant effect on the fatigue life of GH4169. With the increase of stress concentration factor, the fatigue life decreases significantly. When f is 0.13 mm/r, the surface stress concentration factor K_st is 1.166; the surface micro-hardness is 405.27HV_0.025; the surface residual stress is 82.08MPa; and the average fatigue life is 6.98×10⁴ cycles. The multiple cracks are initiated at the machined surface defects of GH4169 superalloy specimen.

Three continuous silicon carbide fiber reinforced SiBCN composites (SiC_f/PyC/SiBCN) distinguished by different weaving methods of fibers (including two dimensional woven, 2.5 dimensional woven with the fiber tow through the thickness and three dimensional five directional braiding) were fabricated by resin transfer molding (RTM), polymer impregnation and pyrolysis (PIP) technology. In order to study the impact of waving methods, the microstructures of fabricated composites were observed and the mechanical properties such as tensile, compression strength and bending strength of the composites were tested. The results show that different distributions of fibers on different directions lead to anisotropy of mechanical properties for each composite, and fabric preform structure has a significant influence on the mechanical properties of the composites.

The effects of low angle grain boundaries on the mechanical properties of second generation single crystal superalloy DD5 were investigated and the test specimens were prepared by using seeds. The results show that at 870 ℃, the yield strength and breaking strength showed no difference when the angle is below 16.1°. The elongation is higher than 15% when the angle is below 11.4°, but the elongation decreases quickly when angle is above 11.4°. At 980 ℃/250 MPa, the rupture life is higher than 130 h when the angle is below 5.1°, and decreased slowly when the angle is above 5.1°. The rupture life still remaines 85% when the angle is 14.8°. But the rupture life decreases quickly when the angle is above 14.8°.At 1093 ℃/158 MPa, the rupture life is higher than 30 h when the angle is below 5.1°, and decreases when the angle is above 5.1°.

According to the ageing problem of laminated transparency, the trasparent polyurethane film used as interlayer had been irradiated by fluorescent ultraviolet lamp for 0 h, 200 h, 300 h, and 500 h respectively. With the aid of ultraviolet/visible spectrophotometer, FTIR and SEM etc., the color, structure and morphology of the materials were studied. SEM shows that when the irradiation time is increased to 500 h, the film surface cracks. The UV degradation mechanisms are that -CH₂-of the position connecting the O and N from hard segment and the soft segment are easy to oxidize and produce hydrogen peroxide under UV and oxygen, which is furtherly oxidized to CO, and some part of the C-O and C-N bonds is cracked through β scission, and then the materials are fractured.

X-cor sandwich is a new kind of foam sandwich reinforced by Z-pin techniques. Under low velocity impact damage, failure mechanism of X-cor sandwich structure is complex. Failure behavior of X-cor sandwich structure at different energy stages was analyzed, and the effects of the volume fraction of Z-pin implant and the density of the foam core on the failure behavior were also discussed. Z-pin diameter of specimens in low speed impact test was 0.5 mm, and the implantation angle was 22°, and the type of foam and Z-pin implant volume fraction in the experiment was variable.The results show that under 6 J impact energy, the impact energy is mainly absorbed by the panel's delamination. The sandwich contained Z-pin is beneficial to reduce the delamination area, while the delamination area of blank sample increases by 45.1%. The foam density has little effect on the delamination area. The Z-pin fails under 12 J impact energy. The residual compressive strength ratio increases first and then decreases with the increase of volume fraction of Z-pin. The sample has the highest residual compressive strength ratio when the volume fraction reaches 0.42%. As the foam density increases, the residual compressive strength ratio increases. When the energy reaches 18 J, shear crack appears in the foam core, and the crack absorbs most of the energy. The weaker the foam core, the larger the residual compressive strength ratio is, and the more the volume fraction of Z-pin implanted, the lower the residual compressive strength ratio is. The low velocity impact model is also established by numerical simulation, and the result of impact damage is directly transferred and applied to study the residual strength model; the result obtained is 25%~29% higher than the experimental value.

Aluminum foam was fabricated by space-holder method with carbamide particles as space-holder material. The effects of forming temperature, porosity and diameter of pores were investigated systematically. During this process, the electronic universal testing machine combined with digital image correlation (DIC) technique was used to test the properties. The results show that the porosity and diameter of pores can be well controlled by space-holder method. The best sintering temperature of forming Al foam is 650 ℃. Under this sintering temperature, the compressive yield strength reaches 10.7 MPa. With the decrease of pore porosity, both of the compressive yield strength and platform stress increase, so the energy absorption of foam is improved remarkably. When the diameter of pores is below 2.0 mm, the energy absorption of foam is improved slightly with the increase of Al foam diameter. DIC technology can be used directly to characterize the mechanical behavior of foam material, which has a good engineering application prospect.

Based on the data of hotcompressing tests which were carried out at temperature ranged from 1050℃ to 1110℃ and strain rate from 0.01s-1 to 1s-1, a system of flow curves of the new type 3rd generation nickelbased superalloy FGH98 was obtained .Then they were used to uncover how the flow stress changes by the change of temperature and strain rate as well as strain.It shows that the curve takes on a typical agitation charateristic and the flow stresses are very sensitive to temperature and strain rate.Subsequently, Arrehenius equation was selected as a model of the constitutive relationship, and the relative parameters were figured out by linear regression analysis of the experimental data with simple error analysis.Then the constitutive equation has been established.

The simulations of the notched specimens under multiaxial loading were conducted by finite element method. The simulation results show that the stress gradient increases with the decrease in notch radius for the same strain path. The equivalent strain method is used to predict the fatigue life based on the strain at the notched root. The prediction results are more conservative with the decrease in notch radius. The effective distance is determinated by the stress gradient method, and the effective distances are decreased with the decrease of notch radius for the same strain path. The fatigue life is predicted based on the strain at the effective distance, and the predictions are scattered and unconservative. Combining the test results and simulations, a new method determinating the effective distance is presented considering the strain gradient. Most prediction results are in a factor-2 scatter band.

In order to ensure the performance of the automated fiber placement forming parts, according to the homogeneity of the image of the prepreg surface along the fiber direction, a defect segmentation algorithm which was the combination of gray compensation and substraction algorithm based on image processing technology was proposed. The gray compensation matrix of image was used to compensate the gray image, and the maximum error point of the image matrix was eliminated according to the characteristics that the gray error obeys the normal distribution. The standard image was established, using the allowed deviation coefficient K as a criterion for substraction segmentation. Experiments show that the algorithm has good effect, fast speed in segmenting two kinds of typical laying defect of bubbles or foreign objects, and provides a good theoretical basis to realize automatic laying defect online monitoring.

Self-corrosion and pitting corrosion of 7B04 aluminum alloy at different environment conditions were studied by electrochemical test with simulating surface coating damage on 7B04 aluminum alloy. The forming conditions of pitting corrosion after contacting 7B04 aluminum alloy with TA15 titanium alloy were analyzed by finite element method which was based on the mathematical model of galvanic corrosion. The results indicate that the pitting potential of 7B04 aluminum alloy is influenced by Cl^- concentration and pH value. Pitting corrosion of 7B04 aluminum alloy in self-corrosion condition can occur in neutral solution(mass fraction of NaCl>5%) or in acidic solution(mass fraction of NaCl=3.5%). The potential rises when 7B04 aluminum alloy contacts with TA15 titanium alloy which results in the occurrence probability of pitting corrosion. The occurrence probability of pitting corrosion is increased. The pitting corrosion of 7B04 aluminum alloy initiates and propagates when the area ratio of cathode and anode is greater than 40 in neutral solution(mass fraction of NaCl=3.5%). The potential of 7B04 aluminum alloy decreases slowly with the increase of the distance between cathode and anode, and the decline of the potential is not over 2 mV at distance within 10 m.

The property of the surface layer of twice hole expansion Ti1023 alloy was analyzed by TEM, X-ray and roughness tester, and the strengthen mechanism of the bushing hole expansion was discussed. The results indicate that the roughness(R_a1.722→0.349 μm), hardness(Hv32→38) and residual stress distribution of the hole are improved by twice hole expansion techniques,and the fretting wear fatigue(fatigue limits 385→619MPa) of Ti1023 alloy is improved.

In order to improve the poor leachability of alumina-based ceramic cores, different amount of starch was added to the specimens as pore former. Alumina-based ceramic cores were prepared by hot injection technology using corundum powder as base material, paraffin wax and beeswax as plasticizer, silica powder and magnesium oxide powder as mineralizing agent, wherein the parameters of the hot injection process were as follows:temperature of the slurry was 90℃, hot injection pressure was 0.5 MPa and holding time was 25 s. The effects of starch content on the properties of alumina-based ceramic cores were studied and discussed. The results indicate that during sintering period, the loss of starch in the specimens makes porosity of the alumina-based ceramic cores increase. When starch content increases, the room-temperature flexural strength of the ceramic cores reduces and the apparent porosity increases; the volatile solvent increases and the bulk density decreases. After being sintered at 1560℃ for 2.5 h, room-temperature flexural strength of the alumina-based ceramic cores with starch content of 8%(mass fraction) is 24.8 MPa, apparent porosity is 47.98% when the volatile solvent is 1.92 g/h and bulk density is 1.88 g/cm³, the complex properties are optimal.

The post emulsifiable and water-washable fluorescent penetrant testing were carried out with ZL-27A and ZL67 respectively. Ultrasonic cleaning by detergent were used for 30 minutes before penetrant. The parts were immersed and drained for 60 minutes. The macroscopic and microscopic characteristics of cracks were researched using the split mirror and scanning electron microscope. The results show that the outgrowth of high temperature oxidation plugs up the forging cracks. Thus the penetrant testing is not effective in detecting this type of cracks.

The strengthening and toughening mechanism of aluminum lithium alloy treated by thermo-mechanical processing have been summarized, and the effect on the evolution of microstructures, grain structure and precipitation, were discussed and analysed deeply. The precipitation sequence and behavior of the main precipitation phase were modified by the thermo-mechanical processing, stimulating the forming of fine dispersion combined particles of δ', θ"/θ', T1, and S"/S' phases, uniformly distributed in the matrix, which significantly improved the relationships of strength and the plastic toughness, with the inhibiting of broadening of precipitate free zones, and of the precipitation and coarsening of strengthening particles at the grain boundary.The density of solute atom and vacancies significantly raised up after solution treating, and retained as supersaturated solid solution after water quenching, which acted as the driving force for the precipitation during subsequent aging. Pre-deformation and pre-aging significantly increased the density of fine dispersion strengthening particles of δ' and G.P. zones, which uniformly nucleated in the matrix, and the combined strengthening phases of δ', θ"/θ', and T1 were obtained after high temperature second aging, controlling the size and volume fraction of these particles.Refined grain and optimal grain structure were achieved by new and typical thermo-mechanical processing, and the proportion, size, and oriented relationship of main strengthening particles of δ', θ"/θ', and T1 phases were optimized.At last, the research direction of new thermo-mechanical treatment on the large scale rolled plates and hot worked forgings is pointed out, such as age forming, to meet the need of light high performance of new aluminum lithium alloys used for the large aircrafs and heavy lift launch vehicles.

With the size of thin-film electronic devices decreasing, the film stress became an important reason for the failure of thin film devices. Film stress not only affected the membrane structure, but also associated with film optics, electricity, mechanics and other properties, therefore film stress turned into one hot spot in the research field of thin-film materials. This paper reviewed the latest research progress of film stress, substrate curvature method, X-ray diffraction technique and Raman spectroscopy, several frequently used stress measuring techniques were compared and analyzed, and composition ratios of thin film, substrate types, magnetron sputtering process parameters (sputtering power, work pressure, substrate temperature) and annealing etc. factors influencing thin film stress were summarized. It was found that substrate curvature method was suitable for measuring almost all kinds of thin film materials. X-ray diffraction and Raman spectroscopy were just fit for measuring materials with characteristic peaks. Nanoindentation method required extra stress-free samples as comparison experiments. During film fabrication and annealing process, film stress usually transited from compressive to tensile status, and several factors combined together could affect stress, so film stress could be reached the minimum value or even stress-free status through setting appropriate parameters. Finally, combined with film stress research status, accurate stress measurement methods for different materials as a thin-film stress research direction were introduced, and challenges in thin film detection range were pointed out.

Four kinds of C/C-SiC composites were fabricated by isothermal chemical vapor infiltration (ICVI), and the 2.5D needle-punching carbon felt was taken as the preform. The volume fraction of carbon fiber in felt is 30%. The density of C/C-SiC composites is similar (1.87-1.91 g/cm³), while the weight ratio of SiC is decreased from 56% to 15%. The microstructure and phase composition of C/C-SiC composites were observed by SEM and XRD respectively. Friction and wear behavior of the C/C-SiC composites were investigated with the MM-1000 friction machine. The results show that the average macro hardness of matrix is decreased from 98.2HRA to 65.1HRA with the decrease of SiC content from 56% to 15%, and uniformity of hardness distribution is significantly decreased. Finally, by the analysis of microtopography of friction surface and wear debris, it is found that the superficial hardness has an obvious influence on mechanism of wear during braking process. The wear mechanism of the C/C-SiC composites transforms from grain wear to the combination of grain wear and adherent wear with the decrease of surface hardness. At the same time, the average friction coefficient and mass wear rate is increased obviously during breaking process.

In order to improve the anti-wear properties of 300M super-strength steel for aircraft landing gear shock absorbing strut, and to break through the technical bottleneck such as cracks induced by the excessive temperature gradient in laser cladding wear-resistant anti-corrosion self-lubricating coating, the "birth and death" method and the APDL procedure of ANSYS were used to simulate the molten pool's thermal cycle for the 300M super-strength steel's laser cladding wear-resistant anti-corrosion self-lubricating coating. The change of thermophysical parameters with different temperatures for self-lubricant and wear-resistant materials , latent heat in phase change, external heat exchange during laser cladding, laser cladding power, laser cladding scanning velocity and other factors, which affect the temperature field, molten pool, temperature gradient during the laser cladding process were considered. The results indicate that the melting of the substrate requires a combination of laser and molten powder, etc. to bring the effective energy conducted to the region reach the critical value of melting, the increase rate of the melting height of the substrate decreases first and then increases with the increase of the laser power, the decrease rate of the melting height of the substrate decreases first and then becomes larger with the increase of the laser scanning speed. Due to the comprehensive factors of different temperatures and cooling rates in different laser cladding areas, the vertical section of the laser cladding wear-resistant anti-corrosion self-lubricating coating bath is a spoon-shaped molten pool. With the increase of the laser power, due to the difference in the temperature response of the energy input to different regions of the cladding layer, the temperature gradient in the Z-direction and the maximum cooling rate increases. With the increase of laser scanning velocity, the laser input energy decreases, which decreases the combined effects of high-temperature region temperature and rapid local heating of the laser. Meanwhile, the temperature gradient in the Z-direction decreases. Under the condition of maintaining the bonding strength of the cladding layer, the substrate melting zone can be controlled to minimize and lower the temperature gradient by controlling laser parameters reasonably.