It is well–recognized that low Σ-CSL boundaries are highly populated in the grain boundary character distribution (GBCD) for austenitic stainless steel (SS) processed by low strain and subsequent annealing. However, large–strain plus annealing typically tends to introducing numerous random high angle grain boundaries (RHABs) instead of producing high fraction of  Σ3, Σ9 and Σ27 boundaries. In this case, the distribution of grain boundary planes of RHABs must be very relevant to the properties of material. The current study is to explore the evolution of GBCD and grain boundary plane distribution (GBPD) in 304 austenitic SS after large strain and subsequent annealing using electron backscatter diffraction (EBSD) and five–parameter analysis (FPA). After solid solution  treatment, 304 steel samples were separately processed by multiple forging (MF) and direct rolling (DR) with true strain ε=2 followed by same annealing at 900℃ for 2—120 min. Then the GBCDs and GBPDs of the two groups of samples were examined. The results show that the total Σ3ⁿ (n=1, 2, 3) special boundaries in any sample as processed take a length fraction of lower than 45% out of the entire boundaries, and with annealing proceeding the incoherent Σ3 boundaries tend to be tuned into coherent ones and consequently the summation fractions of Σ9 and Σ27 boundaries decrease accordingly. In the two samples which were separately processed by MF and DR but followed by the same annealing at 900℃ for 120 min, their random boundaries or general high angle boundaries (Σ3ⁿ special boundaries filtered) mostly appeare to be the <111>  twist and <110>  tilt boundaries, indicating there exist grain boundary textures (GBT) in both samples. However, in the condition of some misorientations, the GBPDs of random boundaries are quite different in the two samples. For grain boundaries of <111>/30—40^? misorientation, more grain boundaries of twist type nearly on the exact {111} plane are found in the specimen processed by DR and annealing for 120 min (DR120) compared to that processed by MF and annealing for 120 min (MF120). For the grain boundaries of <110>/50^? misorientation, it was found that most of such boundaries in MF120 are tilt type and positioned on {112}, {113} and {115} planes, whereas those in DR120 are tilt or mixed type positioned on {001}, {111} and {012}. It was suggested that there are distinct effects of pre–processing on the GBPDs of annealed 304 steel.

A molecular dynamics simulation of the rapid solidification process of liquid Zn_xAl_100−x (x=25, 50, 75) alloys has been performed, and their microstructural evolutions have been analyzed by means of bond–type index method of Honeycutt–Andersen (H–A) and cluster–type index method. Results show that at the cooling rate of 1×10¹² K/s all rapid solidified alloys are amorphous structures with majority of 1551 bond–type and icosahedronal basic cluster of (12 0 12 0 0 0).In the rapid solidification process, a peak of the number of 1551 bond–type and icosahedronal basic cluster is demonstrated to exist at the special point corresponding to the glass transition temperature (T_g) of alloys. T_g, the glass forming ability (GFA) and the chemical short–range order (PCSRO) drop with the increase in content of Zn of Zn_xAl_100−x (x=25, 50, 75) alloys. Segregation and clustering of Zn and Al atoms in molten and rapid solidified alloys are also detected by PCSRO and visualization analysis.

The effect of sample orientation on static recrystallization (SRX) of AZ31 magnesium alloy was investigated with electron backscattered diffraction (EBSD) technique. Two kinds of samples, one was cut along the normal direction of the sheet (0^? sample), the other along the transverse direction of the sheet (90^? sample), were given 15% uniaxial compression strain at 150℃, followed by annealing at 275℃ for different times. The results show that slip dominates the deformation process during 15% uniaxial compression strain for the 0? samples. However, extension twinning firstly dominates the deformation process and then slip dominates the deformation process during 15% uniaxial compression strain for the 90^? samples. Due to the different deformation mechanisms, the deformation stored energy of the 90^? samples is lower than that of the 0^? samples. As a result, the initiation and completion of SRX of the 90^? samples are significantly retarded compared with that of the 0^? samples. As SRX proceeds, the percentage of low angle grain boundaries between 2^? and 4^? decreases dramatically and a peak located around 30^? appears in misorientation angle distribution map for both the 90^? samples and the 0^? samples. Most SRX grains nucleate at the original grain boundaries for both the samples. A few SRX grains nucleate within extension twins.

Crack initiation, coalescence and propagation normally occupy more than 70% the fatigue life of most engineering structure in the whole fatigue damage process. Investigation on the influence of final machining methods, such as surface rolling, on short fatigue crack behavior for LZ50 axle is beneficial to the manufacture and maintenance of corresponding railway axles. After rolling, the surface hardness increased from 201.68 HV0.1 to 222.90 HV0.1. Much higher residual compressive stress was also engendered in surface and sub–surface by this machining method. Totally six smooth hourglass shaped specimens with surface rolling were tested by a replica technique. The characteristic two–stages behavior, that is, the micro–structural short crack (MSC) stage and the physical short crack (PSC) stage, during crack initiation and propagation was revealed. In MSC stage, the growth rate of dominant short crack for all specimens decelerated twice clearly due to different microstructural barriers. This behavior was related to the restraint of ferrite grain boundary firstly and then to the constraint of pearlite banded structure. While in PSC stage, the decelerating trend was no longer obvious with the increasing dominant crack size. With a given dominant crack size, the crack growth rates of surface rolled specimens were much slower than those of specimens without surface rolling. This difference could reach 1 order of magnitude in MSC stage. Meanwhile, the average fatigue life of the former was about 5.4 times longer than that of the latter. The effective short fatigue crack density of surface rolled specimens increased in MSC stage, then attained the peak value at the turning point between MSC stage and PSC stage, and finally decreased in PSC stage. At the same time, surface rolled specimens owned much less crack density than specimens without surface rolling during the whole fatigue process. Surface rolling can restrain the nucleation and connection of micro–cracks, improve the local microstructure conditions, push back the transition point between MSC and PSC stages, and thus improve the anti–fatigue performance of material. Finally, the reasonable assumed distributions for three kinds of characteristic parameters, i.e., dominant short crack size, fatigue life fraction and effective short crack density, were determined. In general, the dispersion of above data was high in initial stage and relatively low in later stage during crack initiation and propagation process.

Irradiation embrittlement of reactor pressure vessel (RPV) steels is one of the critical issues for integrity and safety in long–life operation of light water reactors. The embrittlement is attributed to three main nano–scale microstructural features including copper rich precipitates, matrix damage and grain boundary segregation. The relevance of matrix component of damage can be high in low copper content alloys and also in the case of high doses. Some recent works have been done in trying to clarify the exact nature of this component of the damage in irradiated commercial steels. This is still an open question: how the irradiation–induced microstructure will evolve in the A508–3 steel in the high dose range. In the present work, in order to emulate the neutron irradiation damage in the RPV steels, 190 keV proton irradiations were conducted on a A508–3 steel to 0.108, 0.216 and 0.271 dpa at room temperature. The irradiation –induced microstructure was examined by TEM. The obtained results show that the irradiation induced defects are mainly dislocation loops, majority of which are both of <100> type and of interstitial type, without the observation of the micro–voids. Dislocation loops distribute roughly evenly in the matrix, and some dislocation loops decorate the pre–existing dislocation lines. As the irradiation dose increase, the average diameter of dislocation loops increase and the size distribution of dislocation loops become broader. As the dose increased from 0.108 dpa to 0.216 dpa and 0.271 dpa, the average diameter of loops increase from about 1.8 nm to about 3.0 and about 4.6 nm, the number density of loops are in the order of 10²² m⁻³ with an weak increasing trend. The formation mechanism of dislocation loops and the effect of dose on hardening and embrittlement were discussed. Irradiation–induced dislocation loops cause hardening and embrittlement in the A508–3 steel, which would not saturate at the studied dose range. The dose dependence of yield strength increment and transition temperature shift follows a power law.

Spray forming with a short process chains has been proven to be a powerful tool for the production of high–alloyed materials. Niobium, as a strong former for the carbide, will mainly form primary MC carbides, such as NbC, which can be formed via the reaction between Nb and C atoms at the beginning of solidification, and it can act as the inoculants and refine the cast structure of steel which can mainly form primary MC carbides. M3 high speed steel with or without Nb addition were prepared via spray forming. The effect of Nb on the microstructure of spray formed M3 high speed steel was investigated by SEM, EDX and XRD methods; the friction performances of these two steels were studied by SRV high temperature tribometer and 3D white–light interfering profilometer. The results show that the amount of primary MC carbides can increase sharply while the reduction of the amount of primary M2C due to the substitution of 2% Nb for 1% V (mass fraction) in M3 high speed steel. For the high cooling rate during the spray forming, the primary MC carbides can be refined and dispersed. Large number of primary MC carbides can improve the abrasive wear resistance of M3 high speed steel, but cannot enhance its oxidation resistance; M3 high speed steels containing Nb possess high tempering resistance.

The corrosion behaviors of nuclear grade commercial alloys 690 and 800 were studied by in situ electrochemical measurements using a self–built high temperature and high pressure water loop system, combining with SEM observation and XPS analysis. The results show that the corrosion potentials of alloys 690 and 800 decrease gradually with immersion time increasing, while the immersion time has no obvious impact on the result from electrochemical impedance spectroscopy (EIS). A large number of needle–like oxides have been found on the surface of alloy 690 after being exposed to high temperature and high pressure water for 408 h. For alloy 800, except needle–like oxides, many particle oxides are also observed. For alloy 690, Cr is rich at inner side of oxide film, while it is rich at outer side of oxide film for alloy 800. Alloy 690 shows better corrosion resistance than alloy 800 in high temperature and high pressure water. After immersion experiment, the contents of Ni²⁺, Cr³⁺ and Fe³⁺ ions in the test water solutions are 0.1×10⁻⁶, 0.1×10⁻⁶ and 0.3×10⁻⁶, respectively

Steel flow control in a continuous slab caster mold is effective for preventing entrapments of both mold power and argon gas bubbles and maintaining high slab quality. The steel flow control technology that utilizes a traveling magnetic field to optimize the flow of steel in the mold has been developed and applied. The moving magnetic fields can induce accelerating flow (electromagnetic level accelerator, EMLA), decelerating flow (electromagnetic level stabilizer, EMLS) and rotating flow (electromagnetic rotary stirring, EMRS) according the travel direction of the fields. EMLS mode applies a low frequency alternating magnetic field that moves from the narrow face of the mold to the mold center below the nozzle exits. In this study, the model experiments were carried out using liquid alloy of Pb–Sn–Bi and argon gas to study the two–phase fluid flow in the mold with a low frequency traveling magnetic field. The resistance probe was applied to measure the distribution of gas bubbles below the liquid surface and in the deeper liquid phase in the mold. The effect of various parameters such as magnetic flux density, casting speed and argon gas flow rate on the movement and distribution of argon gas bubbles in the mold was studied. The results indicate that the quantity of gas bubbles near the narrow face increases with increasing argon gas flow rate and casting speed. With imposed traveling magnetic field, the quantity of gas bubbles near narrow face at deep position in the pool was decreased, so the possibility that gas bubbles were entrapped into the solidification shell of the steel can be decreased, and the asymmetrical floating of bubbles along the width of mold for a higher casting speed was depressed, so higher disturbances at the free surface in the mold caused by excessive floating of gas bubbles locally can be avoided. The investigations on the floating of big bubbles revealed that the coalescence and flotation of bubbles can be enhanced with imposed traveling magnetic field, and the floating of big bubbles along the width of mold get more uniformity at 0.12 T.

Ni–CeO₂ nanocomposite coatings were successfully electrodeposited from a standard Watts–nickel solution by a pulsed current (PC) method under ultrasonic field (UF). The surface morphology, microstructural evolution and phase composition of both pure Ni and Ni–CeO₂ coatings were characterized using E–SEM, TEM and XRD, respectively. The curves of oxidation kinetics and DSC analysis were employed to evaluate high temperature oxidation resistance and thermal stability of these coatings. The experimental results indicate that the effect of acoustic streaming produced by ultrasonic field can effectively promote the uniform distribution of CeO₂ nanoparticles in electrolyte. The adding of 20 g/L CeO₂ can make the Ni grains refined in the Ni–CeO₂ coating. During annealing at 873 K for 2 h, a sort of precipitated phase named NiCe₂O₄ is formed along the edge of crack propagation in this coating to bond or heal up the existing grain–boundaries, and to make them far from the initiation and extension of thermal cracks. A large volume fraction of grain–boundaries act as diffusion channels to make NiCe₂O₄ precipitated and form a continuous and compact layer enriched with Ce alloying element leading to inhibition of mutual diffusion between O and Ni atoms in this layer and reduction of the oxidation rate. According to different endothermic peaks of DSC curves, the activation energy of crystallization calculated by Kissinger equation displays the better thermal stability of 243.3 kJ/mol for Ni grains in the Ni–CeO₂ coating than 159.2 kJ/mol for pure Ni coating, and the corresponding endothermic peak is about 130 K higher than that of the latter.

Thermal barrier coatings (TBCs) are widely used in turbine engines to protect hot–section metallic components from corrosion and oxidation. The typical material of TBCs is 8YSZ due to its low thermal conductivity (2.1 W·m⁻¹·K⁻¹) and relatively high thermal expansion coefficient (1.1×10⁻⁵ K⁻¹). However, at temperature above 1200 ℃, it could hardly be used for long–term application for its low sintering resistance and low phase stability. So it is urgently needed to develop novel TBCs materials with higher phase stability and lower thermal conductivity than 8YSZ. Recently, some materials have been evaluated as the candidates for TBCs, such as LaMgAl₁₁O₁₇ (LMA), La₂Zr₂O₇(LZ), La₂Ce₂O₇(LC) and La₂(Zr_0.7Ce_0.3)₂O₇ (LZ7C3). Among those interesting candidates, the LZ7C3 ceramic shows the promising thermophysical properties for high–temperature TBCs. In this paper, the novel thermal barrier coating of LZ7C3) was prepared by atmospheric plasma spraying. The microstructure, phase structure, composition, phase stability, thermal conductivity and thermal shock behavior of LZ7C3 coating were studied. These results show that the coating had single pyrochlore structure with high phase stability in high temperature. The thermal conductivity of coating is 20% lower than the bulk material due to high porosity of coating. The thermal shock tests indicate that the lifetime and failure mechanism depend on the test temperature. The coatings are failed after 116 cyc thermal shock from 1000  to room temrature, which is attributed to the spallation of lamella. The failure mode of lamella spallation and layer fracture are found when the coating tested at 1100 ℃, the thermal shock lifetime is 53 cyc. whereas at 1200 ℃, the coatings are spalled entirely after 3 cyc thermal shock in the way of layer fractur at the interface between LZ7C3 and bond coat.

The semiconductor properties of the passive film on Ni201 formed by anodic passivation in pH=8.4 buffer solution and the oxide film on Ni201 formed by thermally grown in air at 500 ℃ were investigated by photoelectrochemical response and Mott–Schottky response analysis. The Mott–Schottky plots for both the passive film and the thermal oxide film on Ni201 demonstrated that the two films exhibited p–type semiconductors with different values of flat band potential: 0.40 V for the passive film and 0.15 V for the thermally grown NiO. The photocurrent spectra of the passive film on Ni201 were derived into two peaks for inner NiO and outer Ni(OH)₂ layers, respectively. The band gap energy E_g for the inner NiO was 2.8 eV and the E_g for outer Ni(OH)₂ was 1.6 eV, respectively. The E_g of the inner NiO of the passive film on Ni201 (2.8 eV) was closed to that of the thermally grown oxide of Ni201 (2.4 eV), indicating that the inner NiO in the passive film is crystalline structure. An electronic energy band model of both p–type semiconductors of inner NiO and outer Ni(OH)₂ layers was proposed to explain the photocurrent and Mott–Schottky plots for the passive film on Ni201.

Due to the rapid growth of radio frequency radiation sources, electromagnetic shielding composite materials have become a research hotspot in civil control of electromagnetic radiation technology and military equipment shielding technology. The shielding effectiveness (SE) of these electromagnetic shielding composite materials has much to do with the structures, volume resistivity and magnetic properties of the fillers. Spherical and flaky Fe@Ag core–shell composite particles were synthesized by a liquid electroless plating method in this work. The phase, morphology and chemical composition of spherical and flaky particles were characterized. The magnetic property of fillers was analyzed. The effects of the shape of these shielding fillers on complex permeability, conductivity, magnetic properties and shielding effectiveness of their composition material were investigated. The results showed that spherical and flaky carbonyl iron powders/silver core–shell composite particles both had intact core–shell microstructure. Silver coating of these spherical and flaky composite particles were compact and even. Spherical and flaky Fe@Ag core–shell composite particles both had excellent soft magnetic properties, which shape of composite particles didn’t influence their magnetic properties. Compared with the electromagnetic shielding composite material based on isotropous shielding fillers, spherical Fe@Ag composite particles, the electromagnetic shielding composite material containing flaky core–shell composite particles showed higher complex permeability, lower volume resistivity and higher shielding effectiveness. In the frequency of electromagnetic wave ranging from 30 MHz to 1500 MHz, the shielding effectiveness of the electromagnetic shielding rubber containing flaky particles is –51— –55 dB. And the physical essence of better shielding effectiveness and stronger absorbing loss of composite materials containing flaky fillers was theoretically analyzed.

Graphite–like carbon (GLC) film is a kind of antifriction coating. Cr/Cr–C/GLC and Al/Al–Cr–C/GLC composite coatings were prepared by using an unbalanced magnetron sputtering system on Al–based alloy, where Al and Cr layer are the sublayers, Cr–C and Al–Cr–C are the transition layers. As a comparation, the GLC coating without sublayer was also deposited on the substrate. The microstructure, binding force and tribological properties of as–deposited coatings were studied. The results show that the Cr sublayer shows a columnar growth structure, while the columnar grain is not found in the Cr–C transition layer which has a gradient composition distribution. There is a good combining interface between Al sublayer and Al–based alloy substrate. Al–Cr–C transition layer has a gradient composition distribution also. GLC layers based on different sublayers and transition layers have amorphous structures. Compared with GLC coating without sublayer, the binding forces of Cr/Cr–C/GLC and Al/Al–Cr–C/GLC composite coatings are obviously higher, and the Al/Al–Cr–C/GLC composite coating has the maximum critical load. Under different loading conditions, the friction coefficients of both Cr/Cr–C/GLC and Al/Al–Cr–C/GLC composite coatings are low and similar to each other.

Electron beam surfi–sculpt is a novel surface processing technology, in which electron beam is controlled by magnetic field and deflected quickly over a substrate surface to displace materials in a settled manner, thus producing customized textured surface consisting of an array of protrusions above the original surface and a corresponding array of cavities in the substrate. This technology could be used in dissimilar materials connection between metals and composites, as the protrusions on metal surface would increase the interface area, which results in great improvements in both strength and absorbed energy. It could also be applied to improve the surface coating quality by tailor–making protrusions throughout a component surface so as to enhance the adhesive capacity between coating and substrate, as well as to optimize the stress distribution that occurs in coating process. The application performance of textured surface depends on the microstructure characterisation of protrusions, while the investigation on the microstructures and mechanical properties of the protrusion is lack. In this work, electron beam surfi–sculpt was carried out to produce protrusions on TA15 (Ti–6Al–2Zr–1Mo–1V) surface through multi–beam technique. The microstructure features of protrusions were investigated by OM, SEM and XRD, and the weight percentages of alloy elements were analyzed by EDS. In addition, the micro–hardness of the four zones were measured and the results were explained by its microstructure features and weight percentages of alloy elements. It was found that four zones exist in the protrusion, namely edge zone, central zone, heat affected zone (HAZ) and substrate. The edge zone is composed of coarse grain with platelet martensite inside, whose micro–hardness is the lowest. The central zone, whose micro–hardness is the second lowest, is constituted of coarse grain with regular–layed platelet martensite; however, the grain size is smaller than that in the edge zone. The HAZ is characterized of fine grain with boundary α and parallel–layed short platelet martensite inside, plus the highest micro–hardness. The weight percentages of Al in the HAZ and the substrate were higher than that in the edge zone and the central zone, which, together with different grain size of the four zones, are the two main reasons for the micro–hardness differences of the four zones.

Study on the dynamics of aluminum honeycomb sandwich plates of composite structure material plays a key role for the special applications of the aerospace and automotive engineering. The nonlinear dynamics of honeycomb sandwich plate is explored. According to the classical plate theory and the large deformation, the governing equations of motion are established for the honeycomb sandwich plate subjected to the transversal excitation force by using the Hamilton’s law of variation principle. The transversal damping is taken into consideration. The method of normalization is utilized to transform the nonlinear vibration equations to nonlinear system with double modes of freedom. Numerical simulation is used directly to investigate the nonlinear responses of the honeycomb sandwich plate. The results indicates that the change of transversal excitation force has a significant effect on the vibration of honeycomb sandwich plate because the hexagon cell of core and the amplitude of the first modal are bigger than the second modal. In the different ranges of transversal excitation force, the honeycomb sandwich plate exists different dynamical phenomena. Single periodic motion appears when the force value is small, and periodic motion, multi–period motion, chaotic motion appears with the increase of force. Experiments are conducted to validate the numerical simulation results.

FGH4096 is regarded as a promising powder metallurgy superalloy for high–temperature/pressure turbine disc in aerospace industries due to its high resistance/defect tolerance and high working temperature up to 750 ℃. In the present work, OM and TEM have been employed to study the recrystallization nucleation and microstructure evolution in FGH4096 powder metallurgy superalloy. It is proved that there exist three types of recrystallization mechanisms: nucleation from previous particle boundary (PPB), strain–induced nucleation from butterfly γ' phase (SIP) and twins superposition (TS) nucleation. The physical explanation for this is given from the view of point of micro–segregation, formation of the bend fold boundary and twins superposition, atomic diffusion and dislocation movement.

The cubic γ′ particle morphology evolution was studied during long time aging process in a powder metallurgy (P/M) Ni–based superalloy with Hf addition. The results show that, during long time aging process, the cubic  γ′ particle splits into a doublet of plantes or an octet of cubes. The octet of cubes with low energy is a preferred shape, it splits no longer. The γ/γ′ lattice misfit varies with different Hf contents. The growth or coarsening process of  γ′ precipitate can be roughly divided into interface controlling and strain controlling stages, the  γ′ precipitate morphology is greatly influenced by the elastic interaction energy between  γ′ particles.

Because there are great differences in physicochemical properties and mechanical properties between Al alloy and steel, their joining with high quality and high efficiency is one of difficult problems in study of welding technology. According to their difference in melting point, the brazing–fusion welding technology of Al alloy to steel was developed based on MIG welding. In pulsed MIG arc brazing–fusion welding process, the molten filler metal and Al alloy base metal will form the fusion welded joint, and will form the brazed joint together with unmelted steel plate, which can efficiently prevent the intermetallic compounds (IMCs) from the formation. With the digital pulsed MIG arc welding machine, the brazing–fusion welding of 6013–T4 Al alloy plate to galvanized steel plate was realized with the filler metal of ER4043, and the effect of welding heat input on microstructures and properties of the joint was studied. The results showed that there is a zinc–rich zone in the weld toe of fusion weld in the brazed–fusion welded joint, which is composed of Zn–Al eutectic, Al–rich α solid solutions and Fe3Al. Fe–Al IMCs layer on the brazed interface is 1.05—4.50 μm in thickness and become thicker with the welding heat input being increased. Fe–Al IMCs with sawtooth or tongue shape grow towards the weld, which mainly includes FeAl₂, Fe₂Al₅ and Fe₄Al₁₃. With the welding heat input being increased, the tensile strength of the brazed–fusion welded joint firstly increases and then decreases. At the welding heat input of 850 J/cm, the tensile strength of the brazed–fusion welded joint can be up to 229 MPa and the ductile fracture appears in the HAZ of Al alloy. At the lower welding heat input, the brittle fracture easily occurs.