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FV520B stainless steel is an important material for compression turbine impellers. Its corrosion resistance at high temperatures is critical for the manufacturing and service reliability management...

Mg-based alloys were prepared by rapid solidification of twin roll casting (TRC) which shows that the Mg-RE alloy expressed the quasi-amorphous phased and fine crystalline phase dual-phase material. Corrosion behavior of Mg-Based alloy in 3.5% NaCl solution after 48h immersion and mechanical properties were investigated. The result show that The Mg-RE alloy strip exhibited good corrosion resistance and higher ultimate tensile strength and elongation comparing to the AZ31 alloy strips. The elongation of Mg-RE alloy strip is also high than the AZ91 and ZK61 under powder metallurgy processing. These indicate that Mg-RE alloy produced by our method has a better ductility. This may due to the special microstructure of the Mg-RE alloy forms, i.e., quasi-amorphous phase plus fine crystalline phase dual phase state.

In this study, Mg-based alloys were prepared by rapid solidification of twin roll casting (TRC), then microstructure and element distribution were investigated respectively with Scanning Electron Microscope (SEM) and Electron Probe Micro Analyzer (EPMA). What’s more, in order to analyze microstructure and crystal structure of Mg-based alloys, experiments on specimens with the usage of X-ray diffraction (XRD) and Transmission Electron Microscope (TEM) were also carried out. At last, the designed Mg-Re magnesium alloy with quasi-amorphous phase plus fine crystalline phase dual phase microstructure produced with our rapid solidification of TRC process. The rapid solidification process realized with a faster casting speed and a thinner roll gap that does not need any anther additional devices and vacuum environment. EPMA results and TEM analyses show that the quasi-amorphous phase has a high concentration in Al and RE element. There are quasi-amorphous phase in the middle of Mg-Re alloy cross section surrounded by dendrites phase and normal crystals. Acknowledgement. This work was supported by Cooperative Research and Development Center for Advanced Materials (CRDAM) funded by the Institute for Materials Research (IMR), Tohoku University (Project Number 18G0042).

Magnesium alloy is honored as green engineering material for its low density, high specific strength, high specific rigidity, well cutting processing property, well electromagnetic shielding property, heat conduction and easy to recycle. In this paper, AZ31 Magnesium alloy sheet at difference thickness were prepared by symmetric and asymmetric rolling employed with six-roller mill. Microstructure of the two kinds of rolling magnesium alloy thin sheets at 0.5mm thickness were investigated. The grain distribution of AZ31magnesium alloy sheets made by asymmetry rolling at room temperature are more uniform than those made by symmetry process. The grains made by asymmetry are more tiny and the tensile strength and elongation increased obviously and the mechanical properties got better. At room temperature, value of n increased. Large value of n benefit to stamping forming. At room temperature, the value of LDR of asymmetry rolling sheets is 1.26, which was higher than symmetry rolling. So asymmetry rolling benefits to stamping forming.

A diffusion/transformation coupled model has been developed which combines finite difference (FD) model with a phenomenological model. The composition of the different iron-nitrogen(Fe-N) hardening phase can be regard as a function of nitriding time and nitrogen concentration. The diffusion model and transformation model are linked by the limiting nitrogen solubilities and the effective diffusion coefficients. The effect of alloy elements (Cr, Mo, Mn, V, Ni etc.) is considered by introducing an alloy coefficient for limiting nitrogen solubilities and diffusion coefficient. The diffusion/transformation model can predict nitrogen concentration, phase composition and hardness distribution. The model is employed to simulate the nitriding process of SCr420H low-alloy steels. The simulated nitrogen concentration and hardness profiles are consistent with the measured ones. In addition, the predicted depth distributions of iron-nitrogen phase agree well with the available experimental results. Therefore, the comparison shows the reliability of the coupled model. It can be applied to improve the nitriding process parameters.

Phase field method (PFM) was employed to investigate the crystal growth of Mg-Al alloy, on the basis of binary alloy model, the fluid field equation was coupled into the phase-field models, and the marker and cell (MAC) method was used in the numerical calculation of micro structural pattern. In the cast process, quantitative comparison of different anisotropy values that predicted the dendrite evolution were discussed in detail, and when the fluid flow rate reaches a high value, we can see the remelting of dendrite arms.

A numerical simulation method is used to predict the depth distribution of martensite and hardness in the case layer of carburizing (carbonitriding)-quenched 20CrMnTi steel. Microstructure and mechanical properties of 20CrMnTi steel after carbonitriding and subsequent induction hardening is investigated. The results show that the microstructure after nitriding and subsequent induction hardening is main tempered martensite and nitrides; after carbonitriding and subsequent induction hardening is main martensite and a small amount nitrides. The simulation results were a little different from experimental results. According to the results, the factors of reducing the accuracy of the numerical simulation method have been discussed.

A layer of Mo (Si,Al)2 was prepared on the sample surface of Mo substrate by powder coating method using Al-Si mixed powder and then diffusion reaction in argon atmosphere at 900°C. The results of oxidation resistance showed that the Mo samples coated with the Mo (Si,Al)2 layer had an excellent oxidation resistance in air even at 1200°C. The reason of oxidation resistance is the formation of a dense alumina film on the sample surface. Therefore, the further oxidization of the sample can be prevented. In addition, The formation of Mo5(Si,Al)3 layer was also observed at the interface between the Mo substrate and the Mo (Si,Al)2 layer.

In order to develop a new air cell cathode, the mixed with Mg alloy and zinc powder as anode material of a kind of button battery was proposed in the research work. In this paper, the ion concentration results of corrosion solution by ICP measurement was used electrochemical simulation by FACSIMILE for evaluating mechanism of corrosion reactions for Mg alloy and Zn mixed button cell.

A modified 2-D CA model has been developed to simulate dynamic recrystallization behavior of Magnesium (Mg) alloy during hot deformation processing. Based on the fact that Mg has an HCP crystal structure with six-fold symmetry, the model employs the hexagonal CA lattice. The initial microstructure with prescribed grain size was generated by a normal grain growth algorithm. The DRX model consists of dislocation density evolution model, DRX nucleation model and recrystallization grain growth model. DRX grain morphology and size, flow curve were simulated by the present model. The calculated results were compared with the available experimental findings in AZ31 Mg alloy, the predictions show very good agreement with the experimental results.

In this paper, in order to study the transformation plasticity behavior of steel materials in heat treatment and other heating manufacturing process, experiment and simulation of heat treatment for SUS420J2 were carried out. With the conditions of the experiments and simulation, SUS420J2 steel was heating to the austenite transformation temperature and stress is loaded when the steel rapidly cooled to the martensitic transformation start temperature. The transformation plasticity behavior and influence in the load stress of the heat treatment process are revealed.

The purpose of this study was to examine the microstructure and texture evolution of a twin roll cast AZ31 magnesium alloy after multi-pass warm rolling in a temperature range from 233 to 248 °C. Reduction per pass was kept constant at about 10% and the total reduction was 98.2% after 33 pass steps with a change of sheet thickness from initially 2.85 mm down to 50 μm. The rolled sheets exhibited a fairly strong basal texture with an intensity of 17–21 multiples of random distribution (MRD) in the initial stages (with a thickness above 0.47 mm) due to the lower rolling temperatures. The basal texture intensity decreased to 13–15 MRD in the later stages (with a thickness below 0.3 mm) due to the occurrence of dynamic recrystallization at slightly higher rolling temperatures to balance out the demand of rolling force. The basal pole in the thicker sheets spread slightly along ±TD with an ellipse shape mainly due to the activation of 〈 a 〉 prismatic slip and the occurrence of shear bands, while the splitting of basal pole in the thinner sheets was observed to be along the RD with a tilting angle of about ±10°. This was attributed to the activation of 〈 a + c 〉 pyramidal slip. The average grain size in the thinner sheets in the later stages during the multi-pass rolling decreased almost linearly with increasing number of rolling steps. This could be explained via a change in the Zener–Hollomon parameter which was associated with the strain rate affected by the sheet thickness during rolling at a constant percent reduction.

Fe 76 Si 9.6 B 8.4 P 6 amorphous powder was produced by gas atomization. Next, bulk amorphous powder discs were prepared by pressing a mixture of Fe 76 Si 9.6 B 8.4 P 6 amorphous powder and a small amount of SiO 2 powder using the spark plasma sintering technique. The resulting bulk amorphous powder cores were obtained from the compacted discs using an electrical spark erosion machine. The powder core with 5 mass% SiO 2 shows both high saturation magnetization of 1.41 T and good soft magnetic properties, 23 A/m for coercive force and 117 for effective permeability at 1 kHz. The core also exhibits much lower core loss than silicon steels or the powder core without SiO 2 , only 71 W/kg at a maximum magnetic induction of 0.2 T with a frequency of 10 kHz. The low core loss is due to a SiO 2 insulator layer forming on the surface of the alloy powder that can effectively reduce the eddy current and consequently reduce the core loss.

To better understand the twin-roll casting process, based on the analysis of the solidification phenomenon, the geometry shape of the molten metal pool, the continuity of metal and the balance of energy and momentum, five critical partial equations were established separately including the equations of pool level, solidification process, roll separating force, roll gap and casting speed. Meanwhile, to obtain a uniform sheet thickness and keep a constant roll separating force, a decoupling control model was built on the perturbation method to eliminate the interference of process parameters. The simulation results show that the control model is valuable to quickly and accurately determine the control parameters. Moreover, Mg alloy sheets with high quality were cast by applying this model.

Crack initiation and propagation during creep test in a recrystallization (RX) grain containing directionally solidified (DS) nickel-base superalloy was studied by employing electronic backscattered diffraction (EBSD) technique. Creep samples were locally deformed and then heat treated to get local RX at the center of the gauge length. Creep test was carried out at 980 °C/235 MPa. It was found that during creep test, precipitate free zones (PFZ) were formed along the RX grain boundary and the cracks were initiated and propagated along the interface (a) between PFZ and RX grains, (b) between PFZ and the matrix or (c) within PFZ. It indicated that the crack initiation and the propagation were crystal orientation dependent.

A mathematical model has been developed to simulate the nitriding process of plain carbon steel, considering the simultaneous diffusion of nitrogen in different iron-nitrogen (Fe-N) phases and the precipitation dynamics of γ’e and iron-nitride. The model can predict the distribution of nitrogen concentration, volume fraction of Fe-N phases and hardness. Furthermore, a finite element method (FEM) post-process technology is presented to avoid the limit of FEM mesh improvement and time-saving. The uniform-sum-division algorithm is adopted as local refinement algorithm (LRA) of meshes. The modified inverse distance weighting (IDW) method is used to interpolate the FEM simulated results. Then, the nitriding model and post-process technology are incorporated within the framework of the developed FEM code COSMAP (COmputer Simulation of MAnufacturing Process) based on metallo-thermo-mechanical theory. In order to validate the nitriding model and FEM post-process technology, the nitriding process of S30C steel is modeled by COSMAP software. The simulated distributions of nitrogen content and hardness are consistent with the measured ones. In addition, the simulated results at different mesh size are compared for two-dimensional model. It is indicated that the interpolated results agree well with the simulated results of fine mesh model and the experimental ones.Keywords: finite element, nitriding, S30C, iron nitride, inverse distance weighting

The effects of holding temperature and holding time during the spheroidizing annealing on microstructure and mechanical properties of high-carbon chrome steel GCr15 were experimentally studied, especially the ripening process of carbides. The results showed that the spheroidization of carbides was accelerated by optimizing the spheroidizing annealing process. In the case of the same holding temperature, the amount of carbides increases first and then decrease with the increase of holding temperature. The best spheroidizing temperature was about 720°C. Under the conditions of various holding time, the size of carbides and the hardness decrease with the increase of holding time.

This study is aimed to determine the effect of stress corrosion with low strain rates on the electrochemical properties of alloy electrode. Stress corrosion cracking tests of Mg-Zn-In-Sn alloy in 3.5 wt.% sodium chloride solutions at 25°C were performed. The effects of the electrochemical properties under the stress corrosion with low strain rates were investigated. The microstructures of cross section were observed by optical microscope. The results showed that the ultimate tensile strengths of Mg-Zn-In-Sn alloy increased and the strain decreased as the strain rates increased. Open circuit potentials (OCP) of Mg-Zn-In-Sn alloy electrode possess stability and the loop currents (LC) were improved with the increasing of stress in the elastic zone. The variation of OCP and LC did not change with the increasing of strain-rate. The microstructure of cross section observing revealed the mechanism of OCP and LC changing

Directional solidification process can better control the grain orientation and eliminate the horizontal grain boundary, so excellent performance of alloy can be achieved by it. In the paper, the macro and micro analysis were coupled to predict the microstructure growth of magnesium alloys in directional solidification process. FEM (finite element method) was used to calculate undercooling temperature, by which the macro analysis results were coupled into the micro analysis. Phase-field method (PFM) offers the prospect of carrying out realistic numerical calculation on dendrite growth in metallic systems, and it was employed to calculate real dimension of magnesium alloy microstructure in directional solidification. Different magnitude values of anisotropy that predicted the columnar dendrite evolution were calculated. Quantitative comparison of numerical simulation results to the experiment analysis were carried out. The microstructure obtained by PFM is in good agreement with the actual pattern by the optical microscope observation.

The study is diffusion bonding of Mg-AZ31 and Al-6061 under pressure and no pressure by using the direct bonding method. After bonding process, characteristics phase in interface and bonding boundaries of Mg-AZ31/Al-6061 were characterized . The diffusion formation was observed by SEM. Aluminum solid solution and Mg17Al12 alloy phase was proved by analysis of XRD. In the process of measurement, crystalline structure of nearby interface characteristics phase was analyzed in detail by TEM. Based on the above analysis, the crystal model of the magnesium alloy and aluminum alloys was established under pressure, and the bonding mechanism was discussed. The results show that the bonding materials could be bonded under no pressure and the structure of bonding interface is more optimized than pressure.

Thermal flow finite element simulation was carried out to deeply understand the solidification and deformation phenomena of magnesium alloy in molten zone during twin-roll casting process. The results show that temperature near the nip of the rolls is about 680K based on current conditions, and there are two vortexes in the molten pool during casting, a peak formed at solidus. Due to the metal flows in molten pool and relative rotates of the rolls, temperature field of molten zone is different from normal casting, which will cause the solidification structure changes. An experiment by using a vertical type twin-roll caster was also conducted, and the amount of deformation bands at the joint line is larger than that at the two sides. Substructures can be found due to dynamic recrystallization during casting process.

This paper studies mainly the diffusion bonding of 3Y-TZP/SUS304 by using the chemical bonding method. In the bonding interface of 3Y-TZP and SUS304, the Ti-Cu powder/sheet was used as bonding materials. In bonding process, multi-alloy with Fe-Ti and Fe-Cu have been confirmed by Electron Probe Micro-Analyzer (EPMA) determination. Through the microstructure observed by AFM and SEM, bonding boundaries of 3Y-TZP/SUS304 by Ti-Cu powder/sheet had good formation. The distribution of the residual stress on near interface was measured by XRD method. By using of these results, the mechanism of the ceramic and stainless steel was discussed.

In order to study the details of deformation and microstructures evolution during rolling and annealing process, magnesium alloy AZ31 blank, cast by unidirectional solidification and then sliced, has been rolled at high temperature with one pass deduction of 50% in a 2-high mill. During the rolling process, the mill was stopped, and the rolled sheet was rapidly cooled by the cold rolls. Samples with full length of rolling bite zone were cut form the semi-rolled sheet. Because twinning deformation can be reserved even the sample was polished and etched. The continuous changes of microstructure, from entrance to exit of roll bite, both rolled and annealed samples, were evaluated by Optical Microscope (OM), Scanning Electron Microscope (SEM). The results revealed that grain refinement mechanism was twinning intersection which segmented large grains into small pieces. The average grain size is 7µm after one pass 50% reduction hot rolling and 350°C, 15min annealing.

This paper is mainly a study the diffusion bonding of Mg-AZ31/Al-6061 by using the direct bonding method. After bonding process, multilayer field with Mg-Zn and Al-Zn have been confirmed by EPMA determination. Through the microstructure observed by SEM, bonding boundaries of Mg-AZ31/Al-6061 had good diffusion formation. The identification of the component on near interface was measured by XRD method. By using of these results, the mechanism of the magnesium alloy and aluminum alloys was discussed.

A modified two-dimensional (2-D) cellular automaton (CA) model was constructed to simulate dynamic recrystallization (DRX) process of GCr15 steel. Particle stimulated nucleation (PSN) was incorporated into the CA model to determine the influence of dispersed particles on the nucleation of DRX. In addition, the model included the effects of particles on increasing the dislocation density and pinning the grain boundaries for accurate determination of micro-structural evolution during DRX. The model was applied to simulate the DRX process of GCr15 bearing steel. DRX grain size and volume fraction were simulated using the CA model. The simulated results indicated that the simulated stable grain size of particle-containing model is closer to measured value than particle-free model. It was observed that DRX kinetics depends on both thermo-mechanical parameters and initial grain sizes. The calculated results were compared with the experimental findings in GCr15 bearing steel, the predictions show very good agreement with the experimental results.

DLC/SiC films (SiC as a transition layer) were prepared on the surface of magnesium alloy (AZ31) using a plasma immersion ion deposition (PIID) process. A dense and smooth DLC film can be observed by SEM. The surface hardness can be improved to 11.45GPa by deposition of the DLC film. Electrochemical tests show that the corrosion potential of AZ31 with DLC film is increased from -1.7V to -0.6V, which indicates that the DLC film improves the corrosion resistance of Mg alloy.

In the present work, Ni/MgO powder was prepared by co-precipitation in which CO restore NiO to elemental subtance Ni due to C2O42- was decompose to CO and CO2 at 700°C. As the process of the second sintering, H3BO3 was added into the sintered powder of 700°C and was grinded. Then the powder of H3BO3 added was sintered at 800°C，so that the powder was refined, obviously. Thermogravimetric analysis (TGA) and differential thermal analysis(DTA) was carried out in CO2 flow at 10°C/min. X-ray diffraction (XRD) was carried out on a X-ray diffractometer operated at 20KV and 40mA. The microstructures and morphologies were studied by EPMA and XPS.

The unidirectional solidification process of magnesium alloy needs to establish a specific temperature gradient in casting mold, the direction of crystal growth and heat flow are in the opposite direction in the unidirectional solidification. The process can better control the grain orientation, and eliminate the horizontal grain boundary, so to attain columnar grain structure and excellent performance of magnesium alloy. In this paper, Numerical simulation is carried out by orthogonal experiments in order to obtain the optimal process parameters according to the actual experimental device. Different process parameters are taken into account, including pulling speed, cooling time and cooling intensity. FEM (finite element method) is employed to calculate the temperature field and reached a straight shape of temperature gradient distribution which is conductive to achieve unidirectional solidification microstructure. PFM(phase field method) is adopted into the microstructure calculation. The microstructure obtained by PFM is in agreement with the actual pattern by the optical microscope observation.

Finite element method was employed to calculate the macroflow velocity and temperature distribution of the pool domain’s biting zone in twin-roll casting. Macroanalysis results were inducted as boundary conditions into microanalysis. Phase field method (PFM) was adopted to investigate the microstructure evolution. Based on the Kim–Kim–Suzuki model, the effect of metal flow velocity was coupled on the solute gradient item, and the real physical parameters of AZ31 were inducted into the numerical calculation. We used the marker and cell method in the discrete element solution of microstructural pattern prediction of AZ31 magnesium alloys. The different flow velocity values that predicted the columnar dendrite evolution were discussed in detail. Numerical simulation results were also compared with the experiment analysis. The microstructure obtained by PFM agrees with the actual pattern observed via optical microscopy.

In order to better understand twin-roll casting process, a 3D finite element method (FEM) simulation was carried out, based on the conditions of the pilot vertical twin-roll caster, to study the thermal flow and solidification behavior in the twin-roll casting process. The simulation results show that non-uniform temperature and velocity distribution near the side dam region are the main reason for causing non-uniform solidification and non-uniform deformation along the cast sheet width. Therefore, it is necessary to preheat the side dams or improve the design of nozzle to compensate the effect of side dams on the casting process. High quality magnesium sheets have been cast after improved the casting devices.

This paper is mainly a study the diffusion bonding of 3Y-TZP/SUS440 by using the chemical bonding method. In the bonding interface of 3Y-TZP and SUS440, the Ti-Cu (brass) powder/sheet was used as bonding materials. After bonding process, multi-alloy field with Fe-Ti and Fe-Cu have been confirmed by EPMA determination. Through the microstructure observed by AFM and SEM, bonding boundaries of 3Y-TZP/SUS440 by Ti-Cu powder/sheet had good formation. The distribution of the residual stress on near interface was measured by XRD method. By using of these results, the mechanism of the ceramic and stainless steel was discussed.

Water jet cavitation peening is applied to improve the strength and mechanical properties of the friction-welded joints of titanium alloys. Scanning electron microscopy observations of the microstructure of the welded joints and welded area before/after water jet cavitation peening confirm slip dislocation at the microstructure near the surface of the specimens. The residual stress on the surface of the welded joint is measured by X-ray diffraction. The results indicate the effect of peening time on the strength of compressive residual stress.

Water cavitation peening (WCP) with aeration is a recent potential method in the surface enhancement techniques. In this method, a ventilation nozzle is adopted to improve the process capability of WCP by increasing the impact pressure, which is induced by the bubble collapse on the surface of components in the similar way as conventional shot peening(SP). In this paper, the process capability of water cavitation peening and shot peening is investigated, The residual stresses in the near-surface and surface morphologies of spring steel SAE 1070 was characterized by X-ray diffraction (XRD), optical microscopy (OM). After peening treatment, changes in surface morphologies, as well as residual stress with the different peening duration were recorded. The obtained results indicate that the WCP processing had a better surface finish than SP processing.

Water cavitation peening (WCP) with aeration, namely, a new ventilation nozzle with aeration is adopted to improve the process capability of WCP by increasing the impact pressure induced by the bubble collapse on the surface of components. In this study, the influence of water cavitation peening (WCP) treatment on the microstructure of spring steel SAE 1070 was investigated. The microstructural evolution in the near-surface of spring steel SAE 1070 as a function of WCP time was characterized by X-ray diffraction (XRD), optical microscopy (OM). After WCP treatment, changes in the microstructure, as well as residual stress and surface morphologies as functions of WCP time, were recorded using a novel experimental design involving an in-situ observation function. The obtained results indicated that the refinement grains were induced by WCP in the strengthening layer. A stable compressive residual stress layer was found in the near-surface of the investigated spring steel SAE 1070.

The γ-Al203 and AgCl/Al203 catalyst powder were coated on a stainless steel substrate by dip coating and electrophoretic deposition method. And AgCl/Al203 catalyst was produced by three kinds of methods, and the difference between the NOx reduction catalysis of the coated sample was compared. XRD and SEM were used to study the crystalline structure and cross-section of the coatings. The coating of γ-Al203 with the thickness of 3-5 μm and AgCl/Al203 catalyst with the thickness of 5-9 μrn were made on the surface of SUS304 plate without exfoliation. The NOx conversion of the coated sample with catalyst was about 70% at the maximum.

A new magnesium alloy anode is based on an environmentally friendly electrode that contains none of mercury, lead and chromate, but it can enhance the electric properties of alloy significantly. Magnesium alloy adding eco-friendly elements Zn-In-Sn which was developed by orthogonal design were obtained by two casting methods. The effect of additive elements on performance of electrode material was studied. The effects of elements addition and casting method on electric properties and corrosive properties of Mg-Zn-In-Sn alloys were investigated by using electrochemical measurements, corrosive tests and observation of surface structure. The results show that Mg-Zn-In-Sn alloy anode has higher electromotive force and more stable work potential than that commercial magnesium alloy AZ91. It is suitable for anode material of magnesium battery for its small hydrogen evolution, less self-corrosion rate and easy to shed corrosive offspring off.

Using finite element analysis software of COSMAP, a three-dimensional elastic-plastic finite element model of linear friction welding (LFW) process of Ti6Al4V alloy was established. Based on metallo-thermo-mechanical theory relevant to describing the coupled fields of metallic structure, temperature and stress–strain, the temperature fields, phase transformation and stress fields during the LFW process were investigated in numerical simulation. Moreover, the validation experiment was carried out. The results showed that the simulation results of temperature，phase transformation and the residual stress were in good agreement with the experimental ones, which proved the numerical simulation to be reliable.

A two-dimensional modified cellular automaton (CA) model was developed to simulate the dynamic recrystallization (DRX) behaviour during thermo-mechanical processing. It provides a link for multiscale modeling to bridge the mesoscopic dislocation activities with the macroscopic mechanical properties. This model is applied to investigate the effect of initial grain sizes on DRX process in commercial pure copper. The simulated results indicate that the stable size of recrystallized grain is independent on initial grain sizes. However, the percentage of DRX is not only related to the thermo-mechanical parameters, but also influenced by the initial microstructure. It is concluded that larger initial grain sizes promote a delay in the DRX occur on commercial pure copper. The calculated results compare well with the limited number of experimental observations and theoretical conclusions.

Water cavitation peening (WCP) with aeration, namely, a new ventilation nozzle with aeration is adopted to improve the process capability of WCP by increasing the impact pressure induced by the bubble collapse on the surface of components. In this study, in order to investigate the process capability of the WCP with aeration a standard N-type almen strips of spring steel SAE 1070 was treated byWCP with various process conditions, and the arc height value and the residual stress in the superficial layers were measured by means of the Almen-scale and X-ray diffraction method, respectively. The optimal fluxes of aeration and the optimal standoff distances were achieved. The maximum of arc height value reach around 150μm. The depth of plastic layer observed from the results of residual stresses is up to 150μm. The results verify the existence of macro-plastic strain in WCP processing. The distributions of residual stress in near-surface under different peening intensity can provide a reference for engineers to decide the optimal process conditions of WCP processing.

Orientations distribution between grains of two high grade pipeline steels were investigated by electron back-scattered diffraction (EBSD). Then the percentage of low-angle grain boundaries was studied qualitatively to analyze the effect of low-angle grain boundaries on the yield-strength ratio of high grade pipeline steels. From the mode of coordinate deformation and the ability to resist deformation by the grain boundaries, the results show that when the effective grain size are almost the same, the pipeline steel which has the smaller percentage of low-angle grain boundaries, the larger difference between the yield strength and tensile strength, which makes the yield-strength ratio of pipeline steel lower.

Comparing with conventional mechanical shot peening (SP) technique, water cavitation peening (WCP) experiments of Almen strips were carried out on a self-manufactured equipment. The results show that WCP demonstrates a wide range of standoff distance (SD) that from the nozzle to the surface of the object. By measuring the colour changes of the Fuji pressure sensing film, over 110 MPa impacting pressure was detected, which is resulted from the bubbles blasting on the sample surface when the SD is from 65 to 100 mm under 40 MPa of operating pressure. 600 MPa compressive residual stress achieved on the suface of the Almen strips after WCPed for 32 min. The depth of the zone affected by the compressive residual stress is about 100 µm. The highest residual stress appears in the top surface layer, while in case of SP it appears in the subsurface. Compared to SP, WCP is capable to get rather smoother surface and cause less deformation of the testing sheet, simultaneously.

Water cavitation peening is a technique similar to shot peening that induces compressive residual stresses in materials for improved fatigue resistance. Generally, residual stress is of two types: macro-residual stress and micro-residual stress. In this paper, a novel combined finite element method and dislocation density method (FEM/DDM), proposed for predicting macro and micro-residual stresses induced on the material subsurface treated with water cavitation peening, is presented. A bilinear elastic–plastic finite element method was conducted to predict macro-residual stresses and a dislocation density method was conducted to predict micro-residual stresses. These approaches made possible the prediction of the magnitude and depth of residual stress fields in pure titanium. The effect of applied impact pressures on the residual stresses was also presented. The results of the FEM/DDM modeling were in good agreement with those of the experimental measurements.

Stress intensity factors of thin AZ31B magnesium alloy sheet under biaxial tension loading were analyzed by modified Dugdale model. K-values with crack angle of 90° obviously show that there is no influence of the loading condition in Mode-I. In the 45° case, KI values are obtained within 10% errors when they are calculated by modified Dugdale model under biaxial loading. It is concluded that the modified Dugdale model is one of effective ways to evaluate stress intensity factor of AZ31 magnesium alloy sheet appropriately.

A new magnesium alloy plate added elements Zn, Sn and In was manufactured by twin-roll continuous casting method to improve the precipitation of AZ91 alloy. The effects of elements addition and casting method on microstructure and mechanical properties of the Mg-Zn-In-Sn alloys were investigated by optical microscopy (OM), transmission electron microscopy (TEM), electron probe micro-analysis (EPMA), X-ray diffractometry (XRD) and energy dispersion spectrograph (EDS). The results show that the Mg-Zn-In-Sn alloy has higher tensile strength and better corrosion protection than the AZ91 alloy. The outstanding precipitation strengthening effect of the alloy is attributed to the small grain size and the hard precipitates between the grain boundaries.

The γ-Al2O3 and AgCl/Al2O3 catalyst powders were coated on a stainless steel substrate and influences of preparation methods on coating and NOX reduction were studied. The stainless steel SUS304 was coated by Electrophoretic Deposition Method using dehydrated aluminum nitrate as a binder. The AgCl/Al2O3 catalyst was produced by three kinds of methods, and the difference in the NOX reduction catalyses of coated samples was examined. XRD and SEM were used to study the crystalline structure and cross-section of the coatings. The coatings of γ-Al2O3with the thickness of 3-5 μm and AgCl/Al2O3 catalyst with the thickness of 3-8 μm were made on the surface of SUS304 plate without exfoliation. The NOX conversion of the coated sample with catalyst was about 70 % at the maximum. Furthermore, there was a peak in NOX reduction at the different temperature in the case of the catalyst produced under the conditions A.

The influence of water cavitation peening (WCP) treatment on the microstructure of pure titanium was investigated. The microstructural evolution in the near-surface of pure titanium as a function of WCP time was characterized by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). After WCP treatment, changes in the microstructure, as well as residual stress and surface morphologies as functions of WCP time, were recorded using a novel experimental design involving an in situ observation function. The obtained results indicate that twinning plays an important role in the plastic deformation and residual stresses of hexagonal close-packed (HCP) structured metal materials, and therein, that the deformation twinning and twinning interaction were induced by WCP in the strengthening layer. A stable compressive residual stress layer was found in the near-surface of the investigated pure titanium.

Twin-Roll-Casting process is a rapid solidification process combining with hot rolling deformation. The liquid metal will be squeezed out but not sucked in from the mush zone caused by rolling deformation. This is different from conventional continuous casting process and will greatly affect the microstructure morphology and surface cracks of as-cast strip. In this paper, a 2D FEM model was employed to simulate the thermal mechanical behavior during twin-roll casting process of Mg alloy AZ31. The FEM results were compared with experimental results and show the effect of rolling deformation on the microstructure morphology and surface cracks of as-cast sheet.

As a novel surface strengthening technique, Water-jet cavitation peening has been applied to improve the fatigue life by inducing the compressive residual stress in the near surface layer of mechanical components. Compared with conventional shot peening, one advantage of WCP is that the complicated and tiny surface can be peened more easily. In this study, the small holes with various diameters and depths in the SUS304 stainless steel specimens were treated by WCP. In order to estimate its strengthening capability to the small holes, the surface residual stress and the depth distributions in the near surface layer of the small holes were measured by X-ray diffraction method. The experimental results show that WCP can successfully improve the near surface compressive residual stress of small holes. The maximum of surface compressive residual stress of WCP state is up to around –450 MPa. The dept of compressive residual stress zone is up to around 125 μm.

Experimental study on downstream rolling process for twin roll casting magnesium alloy strip was carried out. The microstructure of the casting and rolling strip were observed by OM, SEM, and TEM. The effects of homogenizing process, the parameters of rolling process and annealing after rolled on secondary rolling of AZ31B casting strip were analyzed. The results show that the twin roll casting strip are suitable for rolling at 380-420 °C after homogenizing at 400 oC for two hours, the reduction rate of each pass should be controlled lower than 18%. Mg alloy sheets with thickness from 0.3-1 mm can be produced in once annealing period in this way. By controlling the pass reduction and rolling temperature, the fabricated AZ31B Mg alloy sheets can achieve both high strength and good plasticity by grain refining below 10μm. The mechanical properties of rolled strip after annealing at 400 oC for 0.5h-1h could get tensile strength 220MPa and meantime elongation rate 20%.