In order to study the effect of hole extrusion strengthening process on the fatigue performance of Ti2AlNb alloy, a simulation analysis model of residual stress of hole strengthening process was established. The distribution law of surface residual stress and strengthening mechanism after hole extrusion process were discussed. In this work, the hole extrusion experiments were carried out. The high temperature and low cycle fatigue performance of the compressed and un-compressed specimens were tested respectively. Meanwhile, the microstructure characteristics of the fatigue fracture of the two specimens were compared. The results show that the hole extrusion process can produce a strong residual compressive stress layer around the small hole, which effectively delays and inhibits the initiation and propagation of fatigue cracks, and significantly improves the high temperature and low cycle fatigue performance of Ti2AlNb specimens.

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.

In this paper, nano-sized Gd2SiO5 powder was synthesized by a cocurrent chemical co-precipitation method with Gd2O3 and TEOS as raw materials. The thermal behavior of precursor, phase composition and microstructure of the obtained powder were investigated, the synthesis mechanism was also discussed. The results show that lower Gd：Si molar ratio in precursor and higher pH value in reaction system can lead to the formation of Gd9.33(SiO4)6O2 phase. On the contrary, Gd2O3 impurity is formed in the obtained Gd2SiO5 powder. In this study, the relatively pure Gd2SiO5 powder can be synthesized at 1000-1300 ℃ with Gd/Si molar ratio as 20：11 and pH value in the range of 9-10. The obtained powder inhibits irregular morphology with average grain size of 100-200 nm. During the synthesis process, the precursor is generated in the form of —[Si—O—Gd]— network, and then translated to Gd2SiO5 grains, as well as Gd9.33(SiO4)6O2 and Gd2O3 impurities.

In order to analyze the ablation damage law of composite laminates with fasteners subjected to the action of lightning current, the lightning finite element analysis model of fastener-containing laminates was constructed based on the principle of thermoelectric coupling, and the results of lightning ablation damage were analyzed and tested. The results compare the validity of the model. The ablation damage of fastener-containing laminates under different ratios of electrical conductivity, specific heat and thermal conductivity was analyzed. The variation of ablation damage area under different factors was summarized. The results show that the lightning ablation damage of the fastener-containing laminates compared with the fastener-free laminates is more threatening to the safety of civil aircraft. In addition, the electrical conductivity and specific heat of the laminate have a greater impact on the ablation area of the fastener-containing composite laminate. When the two factors are reduced, the ablation damage area will increase to a certain extent， while the thermal conductivity of laminates and fastener properties have little effect on the ablation damage area.

CoCrAlYSi-hBN coating was fabricated using the high-velocity oxygen fuel (HVOF) process under several processing conditions， and the effects of process parameters, gas flow and spray distance, on the microstructure and properties of the coating were investigated in the present paper. The microstructure, hardness, bonding strength and chemical composition of the coating was researched by using scanning electronmicroscopy (SEM), microhardness tester, adhesive strength measuring and energy dispersive spectroscopy (EDS). The results show that with the increasing gas flow, the porosity and h-BN content of the coating are reduced, and the hardness is improved; However, the bonding strength increases first and then decreases due to excessive energy leading serious oxidation. With the increase of spraying distance, the oxide inclusions are increased, which causes the hardness of coatings increase and the bonding strength decrease. In addition, when the spraying distance is 225 mm, the hardness and bonding strength of the coating are the highest due to the low porosity and boron nitride content.