Effect of grain boundary morphology and carbide precipitate on local heterogeneous plastic deformation of a NiCrFe weld metal were investigated by the crystal plasticity finite element method. Results show that the plastic deformation behavior is more homogeneous for the sample with tortuous grain boundaries rather than those with straight grain boundaries, since the tortuous grain boundary can promote the activation of slip systems around it more easily. Owning to the significant differences in the critical resolved shear stress and hardening behavior between the MC carbide and matrix, the carbide has much higher stress and lower strain compared with the matrix. The discontinuous stress distribution at the interface between the carbide and matrix may induce fracture initiation during the deformation. The tortuous grain boundaries and MC precipitates have the opposite effect on the ductility, dipping and cracking of the weld metal. Therefore, it should be tried to obtain the weld metal with tortuous grain boundaries while minimizing MC precipitates for engineering application.

Polycrystalline tungsten (W) plate has been irradiated with low-energy (200 eV) and large-flux He⁺ with the fluences of 1.0×10²⁵-1.0×10²⁶ ions/m² at elevated temperatures of 1023 K and 1373 K in a vacuum chamber of 30 Pa. The mass loss, surface morphology and defects distribution of irradiated W plate were characterized by means of weighing method, scanning electron microscope and conductive atomic force microscope. The results show that the erosion rate of cellular- or nano-fuzz-like areas is lower than 30% of that for the smooth areas on W plate surface. W nano-fuzz can keep the sputtered W atoms from escaping from the surface during large-flux He⁺ irradiation. The W nano-fuzz can act as a self-protective barrier on W-surface against the strong surface erosion under ITER relevant He⁺ irradiation conditions.

The effect of aging temperature on the microstructure and mechanical properties of 00Cr12Ni10MoTi maraging stainless steel was investigated by means of X-ray diffractometer (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), tensile tester and impact tester. The results show that the strength increases gradually with the increase of aging temperature, through the enhanced precipitation strengthening. A large amount of rod-like Ni₃Ti precipitated on the matrix when aged at 500℃, which leads the strength of the steel to the peak value. The impact toughness at room temperature and low temperature decreases with the increase of aging temperature, and the lowest impact energy at low temperature (-196℃) is 51 J for the steel aged at 400℃, while the impact toughness of the steel increases again when aging temperature continues rising to 500℃, which is related to the formation of reversed austenite in martensite matrix. The existence of austenite phase can effectively inhibit crack initiation and relieve its propagation. Aging at 500℃ can effectively exert the precipitation strengthening effect of Ni₃Ti and the toughening effect of reversed austenite, achieving better matching of strength and toughness.

Carbonyl iron powder was taken as electromagnetic wave absorbent, then the epoxy/ ethyl cellulose microcapsule incorporated with carbonyl iron particles was prepared by means of solvent evaporation. The wave-absorbing property, particle size distribution, characteristics of particle and chemical structure of the microcapsules were characterized by means of vector network analyzer, laser particle size analyzer, ESEM-EDS and FTIR. The result shows that the wall material of the microcapsules consists of carbonyl iron powder and ethyl cellulose, thus the wave-absorption properties of microcapsules incorporated with carbonyl iron powder were reinforced. The smaller carbonyl iron powder has a larger interaction area with electromagnetic waves, therefore, the microcapsules incorporated with smaller particle carbonyl iron particles will exhibit better wave-absorption properties. At 18 GHz, the reflection loss of microcapsules without carbonyl iron particles was -1.63 dB, but the reflection loss of the microcapsules incorporated with 50% carbonyl iron particles can reach -5.08 dB and -5.44 dB for the particle size of 3 μm and 0.5 μm respectively, correspondingly, which are 3.45 dB and 3.81 dB lower than that for microcapsule without carbonyl iron particles, besides, the microcapsules incorporated with 50% carbonyl iron particles of 0.5 μm show excellent dispersibility as well.

The styrene (St)/isoprene (Ip) copolymers (S/I) with gradient blocks were synthesized by a one-step anionic polymerization technique with cyclohexane as solvent, n-butyl lithium (n-BuLi) as initiator and tetrahydrofuran (THF) as polar structure regulator. The microstructures and dynamic mechanical properties of synthesized S/I copolymers were characterized by ¹H-NMR and dynamic mechanic analysis (DMA), respectively. The effect of the time of THF addition and St content on the microstructure and the properties of S/I copolymers were investigated. The results show that the time of THF addition had a great effect on the microstructure, mechanical and dynamic properties of S/I copolymers, and the proper time of THF addition may be beneficial to modulate the copolymerization activity of St and Ip, and further modulate the microstructure and composition of the copolymers, therefore, S/I copolymers with gradient blocks could finally form, which possess broadened glass transition region and damping range. The evolution of structure and the properties of S/I copolymers were also analyzed theoretically.

The evolution of microstructure and properties of Fe-15Mn-10Al-0.3C steel during static annealing after different cold rolling treatments was investigated. The microstructure and properties of the test steel were characterized by means of SEM, XRD and EBSD. The results show that during the annealing process, the austenite bands undergo obvious allotropic transformation, whilst γ-phase transforms to α-phase and the amount of transformation increases with annealing time. The isomeric transformation affects the tensile deformation behavior of the annealed steel, the orientation relationship between the α-phase and the γ-phase changed from the neighbor relationship to the K-S with the prolongation of annealing time, which is beneficial to dislocation sliding across phase boundary and improves plasticity. When the annealing time is long enough, the K-S relationship between the two phases loses coherent and the plasticity is reduced. The transformation can regulate the parallelism of the slip system between the α-ferrite and the γ-austenite, which can improve the plasticity of Fe-Mn-Al-C steel.

The effect of N-content on the microstructure and mechanical properties for the simulated coarse-grain heat-affected zone (CGHAZ) of normalized vanadium micro-alloyed steel was investigated by thermal simulation method. The results show that N-content has significant effect on the low-temperature toughness, precipitates, impact fracture morphology and the ultimate microstructure. The steel containing 0.0031% N or 0.021% N has poor CGHAZ toughness. The steel with 0.012% N has optimal CGHAZ toughness. There is slight Ti-enriched carbonitride and grain boundary ferrite in the steel of 0.0031% N, the large-sized ferrite side-plate in the major microstructure can be as the channel of crack resulting the poor CGHAZ toughness. CGHAZ of 0.021% N contains coarse (Ti, V)CN and coarse grain boundary ferrite, the crack can extend along the coarse grain boundary ferrite resulting in poor toughness. CGHAZ of 0.012% N contains thin (Ti, V)CN, the fine grain boundary ferrite and abundant acicular ferrite, which can act as an obstacle to the crack extension, resulting in preferable CGHAZ toughness.

The mixtures of polyamide 650 (O-PA) and benzoxazine were prepared to investigate the effect of O-PA on the ring-opening polymerization (ROP) of benzoxazine and the toughness of polybenzoxazine, while the ROP process of O-PA/benzoxazine mixtures was monitored by means of gelation time measurement, DSC and FTIR. The results show that O-PA could accelerate the ROP reaction of benzoxazine resulting in remark decrease of the gelation time, initial and peak temperatures of ROP of benzoxazine. However, the structures evolution during the ROP process of benzoxazine and chemical structures of polybenzoxazine hardly changed with the incorporation of O-PA. The toughness of polybenzoxazine increased obviously with the addition of O-PA. The addition of O-PA made the thermal stability of polybenzoxazine decrease a little. Thereby, polyamide 650 is a kind of excellent catalysis for benzoxazine.

Composites of SiCf/BN/SiC with micron Al₂O₃ filler were fabricated via precursor infiltration and pyrolysis method (PIP), and then their flexural strength, high-temperature dielectric and microwave absorbing properties were investigated. Results show that as the filler content increases from 5% to 20% the flexural strength of SiC_f/BN/SiC composites increases firstly and then degrades, and the maximum strength can reach 295 MPa. The real part and imaginary part of the complex permittivity of the composites increase with the rising temperature. Due to the introduction of Al₂O₃ filler the values and increasing range of the high-temperature complex permittivity can be significantly decreased with the rising temperature. The composites without filler show poor room- and high-temperature reflection loss (RL), however when the composite possesses 20% Al₂O₃ filler, the room-temperature RL values can be decreased to below -8 dB in the whole X band and its applicable thickness can expand to 3.0~3.5 mm. The RL values can reach -5~-8 dB at 700℃ for the composite with 20% Al₂O₃ filler of 3.0mm in thickness. The introduction of Al₂O₃ filler enhances the design margin for the practical application.

The effect of minor-Cu addition and thermomechanical treatment on the microstructure and properties of Al-Fe alloy was investigated by means of optical microscopy, SEM, tensile test, and conductivity measurement. The results show that Cu was evenly distributed in the matrix of as-cast Al-Fe-Cu alloy, while the Fe segregated at grain boundary. After extrusion the properties of Al-0.7Fe-0.2Cu alloy reached the optimum, the conductivity was 59.90% IACS, the tensile strength was 108 MPa, and the hardness was 31.2HV. The tensile strength of Al-0.7Fe-0.2Cu alloy decreased sharply with the increase of annealing temperature. The tensile strength was the lowest (100 MPa) after annealing at 400℃, while the elongation was the highest (31.3%). The peak electrical conductivity of Al-0.7Fe-0.2Cu alloy was 62.61% IACS after annealing at 250℃. In addition, many fine needle-like θ(Al₂Cu) phase precipitated during annealing in Al-0.7Cu-0.2Cu alloy, which interacted with dislocations. With the increase of annealing temperature, dislocation density decreased and grain refinement occurred.