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Near β titanium alloy is widely used in automotive and aerospace industries due to their high strength-to-weight ratio and high corrosion resistance. The near β titanium alloy can precipitate ω phase and α phase after solution and ageing treatment, the strength of which can be remarkably increased, usually at the expense of ductility. It is one of the most important structural components of load-bearing that usually as aircraft skin, shell plating, main frame, linker and special fastener. The alloy used in this paper is a self-developed Ti-Al-V-Mo-Cr-Zr-Fe-Nb ultra-high-strength β titanium alloy, which is a typical near β titanium alloy. The characteristic of isothermal phase transformation of near β titanium alloys is diversity and complexity, which is sensitive to temperature and directly affects the mechanical properties after ageing. In this paper, the microstructural evolution and mechanical properties of a Ti-Al-V-Mo-Cr-Zr-Fe-Nb ultra-high strength β titanium alloy after isothermal treatment were investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM) and micro-hardness tester. The results show that only the isothermal ω precipitates are formed during ageing at 300℃, and the size of isothermal ω phases increase with the ageing time. The isothermal ω precipitates are first precipitated during ageing at 400℃. With the extension of the ageing time, the α phase nucleation occurs near the ω/β interface. No α precipitates are obtained in the alloy aged at 500℃, and needle-like α precipitates are directly precipitated from the β matrix, which is evenly distributed in the β matrix in a "V" shape. Tensile test shows that the tensile strength of the alloy is 1716.1 MPa and the elongation is 2% after ageing at 400℃ for 12 h. The tensile strength of the alloy is 1439.8 MPa and the elongation is 9.84% after ageing at 500℃ for 12 h, and has a good combination of strength and toughness.

As one of the core hot components of aeroengines, the safe service of turbine blades is crucial to the operation of aeroengines.When the aeroengines encounter some emergency conditions, the turbine blades may suffer overheating, the temperature of which is much higher than the highest normal operating temperature. Overheating can lead to serious microstructural degradation and even premature failure of turbine blades. In this paper,the methods of overheat inspection and failure analysis were introduced, as well asthe effects of overheating on the microstructural degradation and mechanical propertiesof aeroenginesturbine blades. In addition, the damage assessment, life prediction and microstructure rejuvenation of superalloys after overheating were prospected in this paper, which provide a guidance and theoretical basis for the degradation evaluation and failure analysis of turbine blades as well as the development of new superalloys.

Gradient aluminum honeycomb structure is an effective energy-absorbing structure. According to the concept of gradient rate, four types of aluminum honeycomb sandwich components with the same mass and different gradient rates were designed by changing the cell wall length of the honeycomb core layer. On the basis of the same mass, the deformation mode of gradient aluminum honeycomb sandwich structure under quasi-static state, as well as the dynamic response and energy absorption characteristics of layered homogeneous honeycomb structure under impact load and layered gradient honeycomb structure with different gradient rates were compared by combining quasi-static compression experiments and the deformation and mechanical properties of gradient aluminum honeycomb sandwich structures under quasi-static and impact states, which were simulated by nonlinear finite element. The results show that during the quasi-static compression process, the deformation of the aluminum honeycomb gradient sandwich panel has obvious localization characteristics. The deformation of the honeycomb core is preferentially low density until compaction, and the densification strain difference between the layers is gradually decreased as the core layer density is increased. Besides, under high-speed impact, the gradient honeycomb panel is not strictly deformed step by step in the quasi-static process until it is densified. It is the linear elastic deformation, elastic buckling, plastic collapse and compaction that occur as a whole under the interaction of the hammer head inertia and the core layer density. In addition, during the range of the gradient rate designed in this paper, when the gradient rate is γ1=0.0276, the energy absorption of the gradient honeycomb sandwich panel is the best. Compared with a homogeneous honeycomb sandwich panel of the same mass, the energy absorption is improved by 10.63%.

3D printing technology is one of the additive manufacturing technologies for rapid process and manufacture of complex geometric components. Based on the three-dimensional data model, the material is accumulated layer by layer controlled by computer, and eventually forms the solid object. Compared to the traditional manufacturing methods, 3D printing technology has many advantages, such as time saving, low cost, easy operation, no mold and strong controllability of component geometry, etc. Along with the development of this technology, several types of 3D printing technologies, such as fused deposition modeling, selective laser sintering, stereo lithography, digital light processing and solvent casting molding, have been produced according to the core of the printing technology, applicable materials and equipment composition. The principles and characteristics of the four most representative 3D printing forming processes were introduced in this paper, and the research progress of carbon nanotubes to reinforce polymer composites with different types of 3D printing forming processes applied in recent years was summarized. At the same time, it was predicted that the 3D printing molding technology will be developed towards the direction of high precision, industrialization, popularization and high integration in this field, and the research and development of 3D printing materials will also have more prospects.

Additive manufacturing based on PTIG (pulsed tungsten inert gas, PTIG) is a branch of arc additive manufacturing technique. Its notable advantages are low cost, high deposition rate, high material utilization ratio, and suitable for manufacturing parts of large size. In this paper, the research results on the control of formation quality, microstructure and properties of the parts deposited by PTIG additive manufacturing were emphasized in view of experimental research and numerical simulation. Meanwhile, the shortcomings of current investigations were also summarized. Based on accurate prediction and accurate control on the formation quality, microstructure and properties, the research directions for further study on PTIG additive manufacturing technique in the future were put forward, including the influence mechanism of process factors on the formation quality, defects forming mechanism and the suppression measures, numerical simulation on microstructure evolution in molten pool, formation and regulation mechanisms on internal stress and deformation,and the establishment on quantitative relationship model between the microstructure and mechanical properties.

B4CP/PI polyimide composite films with different powder contents and thicknesses were prepared by particle surface modification and wet mixing machinery-thermal imidization method, using high temperature polyimide as matrix and micro-sized boron carbide (B4C) as thermal neutron absorption material. The thermal neutron radiation shielding property, thermal stability and mechanical property of B4CP/PI polyimide composite films were mainly discussed in this paper. It is shown that the micro-sized B4C functional particles can be well dispersed in PMDA-ODA polyimide matrix, and the thermal stability of B4CP/PI polyimide composite films are significantly improved with the increase of B4C content. However, the mechanical properties of the composite films present the opposite trend; meanwhile, the B4CP/PI polyimide composite films exhibit excellent thermal neutron radiation shielding properties, and the neutron permeability I/I0 presents exponential relationship with the increasing thickness of composite and B4C filler particle content. Therefore,through structural design of the materials,the applications requirements in different fields for materials with high temperature resistant and thermal neutron radiation shielding properties can be met.

Research progress of microwave curing on epoxy resin and its composites was summarized on the basis of introducing the principle of microwave curing technology and its advantages. The paper focused on the effect of microwave curing on the curing rate of epoxy resin and its composites as well as the mechanical and thermal properties of cured products. Two suitable composite systems for wave curing of powder-strengthened epoxy and fiber-strengthened epoxy and a few key technological problems for industrial application are introduced. The application prospect of microwave curing on epoxy resin and its composites was also presented.