Based on a new three-dimensional topology-related grain growth rate equation proposed recently by MacPherson and Srolovitz, a set of analytical quasi-stationary grain size distributions were obtained. One of such distribution functions can be used to describe satisfactorily the three-dimensional quasi-stationary grain size distribution obtained from experimental measurement results for pure iron by serial sectioning, and those obtained from computer simulations by vertex method, surface evolver method, phase-field method, Monte Carlo method with Potts model. The corresponding grain size distribution curve is very similar with those of available theoretical quasi-stationary grain size distributions in literature.

Microstructures and hydrogen permeation properties of Nb50Ti25Ni25 and Nb40Ti30Ni30 alloy were investigated, respectively, and compared with Nb, Pd and PdAg alloy. The results indicated that the microstructures of Nb50Ti25Ni25 and Nb40Ti30Ni30 alloy consisted of combinations of the primary bcc-(Nb, Ti) solid solution with the eutectic {bcc-(Nb, Ti)+B2-TiNi}. The volume fraction of the eutectic phase increased with addition of Ni and Ti, in contrast to decrease of the primary phase. The hydrogen permeabilities of Nb50Ti25Ni25 and Nb40Ti30Ni30 alloys at 673K were 1.71×10-8 molm-1s-1Pa-0.5 and 1.03×10-8 molm-1s-1Pa-0.5, respectively, which were in same magnitude level as pure Pd metal, but a little lower than that of PdAg alloy. Increasing of eutectic phase favored resistance to hydrogen embrittlement, while the hydrogen permeability of the alloys increased evidently with the increasing of the primary phase. Alloys with high hydrogen permeability and good resistance to hydrogen embrittlement can be designed by optimization Ni and Ti content.

Three dimensional atom probe combined with optical microscopy (OM) and transmission electron microscope (TEM) was applied to characterize the carbides precipitation and microstructure evolution in Nb-V microalloyed steel plates quenched and tempered at 500冾600 for 4h. The results indicated that, vanadium and niobium were almost dissolved in matrix with slight segregation of carbon in the as-quenched specimen. A cementite was detected in 450 tempering specimen, as well as V- and Nb-containing carbides with difference sizes and number density in 450,550 and 600 tempering specimens. A maximal strengthen effect of this fine precipitates was obtained at 550 tempering. The carbides started to be coarsened and spheroidzed in 650 tempering specimen.

ABSTRACT The effects of Al on the microstructure and stability of GH4169 alloy were studied in this article. When the Al contents were in the standard range required by GH4169 alloy, γ″ and γ′ phase were precipitated separately in the grain, and δ phase was precipitated as the principle precipitate in the grain boundaries. γ″/γ′ “compact morphology” was formed in the grain, δ phase was decreased greatly in the grain boundaries accompanying with a large amount of Laves phase, a small amount of M7C3 carbide and σ phase precipitating there with the increment of Al content, specially above 1.24% (mass.). After long- term aging at 680℃ up to 1000h, γ″/γ′ “compact morphology” grew slowly in the alloys with high Al contents, whereas the amount of the phases precipitating in the grain boundaries was increased, whose sizes were coarsened, and α-Cr phase was formed in this condition. This trend was more obvious with increasing Al contents.

A method for improving the regular solution model by GA-NN is introduced in this article and the activity of component in MnO-SiO2 and CaO-Al2O3 binary system is estimated by this model. Due to the different properties between real solution and regular solution, it is proved that the interaction energy Ωij is the function of temperature and composition, and Ωij ≠Ωji at the same temperature and composition. With the comparison of results received by calculation and previous studies, a high nonlinear capability is found of the model, so it can be used to accurately predict the activity of solution component.

Microstructures of commercial purity copper deformed by high-pressure torsion have been examined by means of transmission electron microscopy. Observations have been carried out in two perpendicular directions, i.e. the longitudinal section and the transverse section. Microstructural observations in the longitudinal section revealed a rather different morphology of the dislocation structures from those observed in the transverse section. In the transverse section, dislocation cell structure was formed at low strains. With increasing strain, the dislocation cells continually transformed into equiaxed subgrains and finally into equiaxed grains with high angle grain boundaries due to dynamic recrystallization processes. In the longitudinal section, at low strains, extended dislocation boundaries were observed. With increasing strain, a lamellar structure was observed with some dislocation cell structured across it. The lamellar boundary misorientation as well as the misorentation between the dislocation cells increasing with shear strain. At median strains, the dislocation cells have transformed into elongated subgrains. At large strain, the subgrains transformed into individual grains and the outline of the lamellar structure disappeared. Compression test results show that an increase in yield stress ( 385MPa) and strain rate sensitivity (0.021) as compared to coarse grain copper.

Plate anode and specimen as cathode parallels with each other, and both are sealed with agents in stainless box. The influence of direct current field (DCF) on nitrocarburizing has been investigated by applying DCF between the anode and the specimen as cathode during the soaking. The test results indicate that DCF can enhance nitrocarburizing, modifies hardness profile along the case depth and save energy. DCF has the heating effect to agents and specimen, which enhances chemical reactions in the agent, accelerates the diffusion of nitrogen and carbon atoms in the specimen. It is proposed that DCF make the concentrations of nitrogen and carbon at and around the specimen as cathode much higher than in any other position compared with the conventional powder-pack nitrocarburizing (CPN) process by forcing nitrogen-/carbon-containing species diffuse toward the cathode, which relatively decreases nitrogen/carbon absorption by inner wall surface of the pack box and the non-working surface of the specimen. DCF’s physical effect of enhancing chemical reaction in the agent increases the activity and productivity of nitrogen-/carbon-containing species, which overcomes the shortcoming that CPN can not produce enough boron-containing species by conventional way of heating.

As-cast Ti-43Al-9V-0.3Y alloy is mainly comprised of γ phase, besides minor α2, B2 and YAl2. The alloy is fine-grained and mainly consists of lamellar structure (approximately 85 vol%). The mean colony size is about 80 μm. There is evidence of the β phase and γ phase along colony boundaries and disperse fine YAl2 particles. There exist some B2 precipitations within the lamellar colonies. As-forged Ti-43Al-9V-0.3Y alloy has the streamline near gamma (NG) microstructure drastically refined with DRX γ grains of 1~5μm. The B2 and YAl2 phases are broken and elongated and the lamellar colonies diminish. As-rolled Ti-43Al-9V-0.3Y alloy has the fine NG microstructure with γ grains of about 20μm. The streamline structure vanishes. The B2 phases with size of 8μm are distributed in the network shape along γ grains and the YAl2 particles are disperse. As-cast Ti-43Al-9V-0.3Y alloy has the ultimate tensile strength of about 510.6 and 425.8MPa, the elongation of 0.5% and 5.7%, at room temperature and 700℃, respectively. After forging and rolling, the tensile properties are greatly improved. At room temperature, the strength of as-forged and as-rolled material increases about 89~132MPa, and the elongation increases from 0.5% to 1% and 1.2%, respectively. At 700℃, the strength as-rolled material increases about 63~72MPa and the elongation increases from 5.7% to 7.9%. The improvement of the tensile properties is attributed to the microstructural refinement and higher density induced by forging and rolling process.

In this paper, the morphology and structure change of fine copper powder during its oxidization process was observed by SEM and TEM. And their weight gain processes were measured by Thermal gravity Analyser(TGA). Based on the experiments and some classical theories, the course of the oxidation of fine copper powder was proposed. Then a new kinetics equation was deduced to simulate the course. The analog results agree well with the data gained from the oxidation of copper between 250-400℃.

The graded material of 316L stainless steel/Ni-based alloy/Ti6Al4V was fabricated from metal powders using laser rapid forming process. The as-formed graded material is fully dense and free of cracks. The microstructure of the graded segment of 316L stainless steel to Ni-based alloy consists of γphase and the hardness values increase with the increment of the content of Ni-based alloy. A series of phase evolutions, , along the graded segment of Ni-based alloy to Ti6Al4V have occurred. The maximum hardness value (HV10830) was measured at the weight ratio of 80% Ni-based alloy to 20% Ti6Al4V, then the hardness values decrease with the increment of the content of Ti6Al4V.

Based on Fourier transient state heating conduction equation, this paper confirms the heating conduction equation of HIPIB. The thermal effect of the target 45# Steel surface irradiated by HIPIB with different power density is simulated. In view of the behavior of ion injection into the metal, thermal load of ion current density were simulated with body heat flux mode and surface heat flux mode. The result with two mode were compared. Another amelioration in the simulation is element removed and reactivated method, which can simulate the evaporation of surface metal under injection by high energy ions. The result show that element removed and reactivated method to simulate disabled element was more alike the forming of crater. The element vaporized on the surface were removed so that the elements around it have been no effect their solidification and cooling. Element removed and reactivated method have little effect in the heating process but improved simulated precision in cooling precess sharply

The flow curves are obtained using single-hit and double-hit hot compression tests carried out on Gleeble-3500 thermomechanical simulator. The change of dislocation density during inter-pass is related to the static recrystallization volume fraction, which can be seen as a function of time. Based on the inverse analysis of the flow curves, a new method to estimate the kinetics for static recrystallization is proposed. Conventional approach using image analyses of quenched microstructure to evaluate the kinetics for static recrystallization can be replaced from this method. The proposed method is applied to the hot compression tests of plain carbon steel, and the kinetics for static recrystallization are obtained successfully for some range of deformation at elevated temperature. The results are clarified by comparing them with that reported in the literature. It is confirmed that the proposed method could provide accurate kinetics for static recrystallization with shorter time for experiment and computation.

A coupling calculation method for welding residual and creep damage has been developed by ABAQUS finite element code and its user subroutine UMAT. According to this method, the effect of welding residual stress for Cr5Mo steel welded joint on creep damage was simulated at high temperature. At the same time the creep damage without welding residual stress was compared with that under the consideration of welding residual stress. The research results show that the maximum residual stress all concentrate in weld metal (WM) and heat-affected zone (HAZ). And the axial and hoop stress is higher than radial stress. At high temperature, although the welding residual stress is much higher at initial stage and the residual stress is relaxed in a short time, the welded joint creep damage is greatly influenced by the residual stress. The distribution of creep damage is same as the distribution of welding residual stress. The presented work provides the probability for the high temperature strength design and life assessment of high temperature component.

The crack tip’s break damage process area of the material like cast iron, can be simplified for crack with cohesive force. To investigate the fracture process of iron and the calculation method of the specimens’ maximum bearing capacity, the three-point bending experiment of eight kinds of size incision specimens were tested, and two of the specimens was measured with electrical strain gages equipment. Through the experiment data, a series of curves were obtained and analyzed, such as the curves of displacement of load point with loading on the typical specimens, and the curve of fracture damaged area deformation with the loading, the relationship curve of beam neutral axes position and loading, the curve of position of cohesive crack tip and loading. The Stress Intensity Factor of the different size fracture specimens was calculated. For different size specimens, the computation method of structure bearing capacity was presented through the stress intensity factor’s computation formula and the fracture criterion. The theoretical calculated value was compared with the tested results, and the relative error of them is not big. Then, the method of estimating structures’ maximum bearing capacity is feasible.

To simplify the preparation process of Tb2Fe17 magnetic intermetallic compound, direct electrochemical reduction of solid pellet of mixture of Tb4O7 and Fe2O3 powder (Tb: Fe = 2: 17) to Tb2Fe17 in molten CaCl2 at 850 oC was investigated. Well stoichiometric Tb2Fe17 powder was obtained through electrolysis at 3.1V for 6h, the oxygen content in the sample was as low as 3900ppm. The reduction process was studied through the composition characterization of the products obtained at different electrolysis times. It was found that Fe2O3 was preferentially deoxidized to metallic Fe within the first hour, and then Tb4O7 was reduced assistantly by forming FeTbx and finally Tb2Fe17 was obtained with the under-potential reduction of Tb4O7 on iron. This was further confirmed by cyclic-voltammetry measurement of a novel Tb4O7 powder filling stainless steel sieve electrode.

The corrosion process of RE steel and carbon steel in 0.3 mol/L NaCl was investigated by electrochemistry impedance spectroscopy test, SEM and X diffraction analysis. The results showed RE could improve the corrosion resistance of carbon steel; compared with carbon steel, the rust layer of RE steel generated in the solution was more compact, the content of α-FeOOH in rust layer with protective effect was higher, the content of activated γ-FeOOH and β-FeOOH was little. The development process of electrochemistry parameter in the equivalent circuit was analysed, the theory of RE improving the corrosion resistance of steel was discussed.

Using the high pure argon gas as carrier gas, the polycrystalline iron fibers with tunable morphology, crystal size and composition were prepared just by controlling pyrolysis temperature of Fe(CO)5. The effects of pyrolysis temperature on the static magnetic properties and microwave electromagnetic properties were studied. The results show that the static magnetic properties and microwave electromagnetic properties of polycrystalline iron fibers are strongly dependent on the pyrolysis temperature owing to the crystal sizes and compositions of polycrystalline iron fibers regularly changing with pyrolysis temperature. the polycrystalline iron fibers obtained at 500℃, with 21.6 nm crystal size and 8.26% C content have the worst soft magnetic properties and the lowest permittivity loss and permeability, however, the polycrystalline iron fibers obtained at 700℃, with 61.1 nm crystal size and 3.88% C content have the best soft magnetic properties and the biggest permittivity loss and permeability loss. The polycrystalline iron fibers with good microwave electromagnetic properties could be obtained by adjusting pyrolysis temperature to control the structures and compositions of the polycrystalline iron fibers.

Sintered Nd-Fe-B magnet with super-high coercivity and high thermal stability was achieved by blending 3wt%Dy2O3 powder and 3wt% (NdDyTb)25(FeCoNbTiGaAl)68B7 powder to near stoichiometric (NdDyTb)12.69(FeCoNb)84.01B6.00 main alloy powder. The intrinsic coercivity Hci with 3028kA/m, the maximum energy product (BH)max with 254 kJ/m3, the temperature coefficient (22-220℃) of remanence and intrinsic coercivity with -0.104%/ ℃ and -0.356%/ ℃, respectively, and irreversible flux loss at 260℃ near 4% were accomplished. Microstructure analyses indicated that that Nd2Fe14B grain boundaries were smooth and straight and the distribution of Nd-rich phase around Nd2Fe14B grain was continuous and uniform. Dy was rich in near the extension layer of Nd2Fe14B grains, indicating Dy element in Dy2O3 powder diffused and substituted Nd element in Nd-rich phase and the extension layer of Nd2Fe14B grains, which increased magnetic anisotropy of boundary of Nd2Fe14B grains only and depressed the nucleation formation and expansion of reverse magnetization domain. Furthermore, ideal microstructural model of Dy distribution in Nd-Fe-B sintered magnets with high intrinsic coercivity was presented.

Cr-O-N films with different chemical composition were deposited using arc ion plating (AIP) between NiCrAlY coatings and the DSM11 substrate as diffusion barriers. The influences of the barriers and the roughness of the substrate on the adhesion of DSM11/Cr-O-N/NiCrAlY were investigated. In general, we observed that the NiCrAlY coating without diffusion barrier has the best adhesion. After including the Cr-O-N films, the adhesion decreased with the increasing oxygen flow rate and the adhesion of the wet blasting substrate is higher than the polishing substrate.

In order to know the penetration of magnetic field in two-stage slitless mold for soft-contact electromagnetic continuous casting, the magnetic flux density and the height of meniscus in two-stage mold and conventional mold were compared through experimental measurement. The results show that (1) the stainless steel cover can prevent the magnetic lines of flux going into mold from the top of mold. It is beneficial to the measurement of magnetic penetration with a cover on the mold. (2) The magnetic flux density increases with the thickness of mold decreasing when frequency is 25000 Hz. The magnetic flux density in two-stage mold is less than that in conventional mold when d=10 mm, but the magnetic flux density in two-stage mold is more than that in conventional mold when d=7 mm, and the penetration of magnetic field in two-stage mold is 4.5 times than that in conventional mold when d=5 mm. (3) The penetration of magnetic field and meniscus in two-stage slitless mold becomes high enough by changing the structural and electromagnetic parameters.

By molten salt electrolysis combined with aquatic electrodeposition, the composite LaNi5/Ni-S film with high stability and HER activity was obtained. The results showed that in the Na3AlF6-La2O3 (92 : 8) molten salt system, although the cathodic potential is much lower than the decomposition potential of lanthanum, the LaNi5 film could be obtained due to the strong depolarization ability of Ni cathode. The composite LaNi5/Ni-S film (η150 = 75 mV, 80oC) could absorb large amount of H atoms, which would be oxidized and avoid the dissolution of the Ni-S film under the state of open-circuit effectively and prolong the lifetime of the cathode.

In the past three decades, the P/M superalloy in our country has a great progress. But in general, there is a big gap between domestic and foreign. The powders are the key. So a novel spark plasma discharge process , different from traditional process such as Plasma Rotating Electrode Process and Argon Gas Atomization, is proposed to produce Superalloy fine powders. Fine powders from wrought superalloy plate and a new P/M superalloy bar are studied.