Grain refinement and texture evolution of a magnesium alloy AZ21 were investigated during multi–directional forging under decreasing temperature from 673 K to 433 K. Dynamic recrystallization (DRX) and texture development were studied at 673 K by OM and SEM/EBSD techniques. The flow curves show rapid hardening accompanied by a stress peak at relatively low strains, followed by strain softening and then a steady state flow stress at high strains. Kink bands with low to medium angle misorientations are evolved at corrugated grain boundaries and also frequently in grain interiors at low strains. Some of them intersect with each other, leading to the fragmentation of original grains. The alignment of the basal planes initially parallel to the compression axis rotated gradually by compression at 673 K and approached an orientation perpendicular to the compression axis at ε=1.2. The relative intensity of texture decreases rapidly with increasing strain to ε=0.4 and goes up later. A similar trend of texture evolution is recognized for the second pass, implying slightly effect of temperature but rather of strain. It is also concluded that increasing the deformation passes can lead to a decrease in texture intensity.

SiCp/2009Al composites were fabricated through powder metallurgy and subsequent extrusion. The phases and elemental distributions in the hot pressed and extruded composites were studied. The slight macro–segregation was found in the hot pressed composite billet. The concentrations of Cu and Mg in the bottom of the billet are somewhat higher than those in the top of the billet. The hot pressed composite contains Al, SiC, Al₂Cu, Mg₂Si and a small quantity of Al₇Cu₂Fe and oxide of Mg. After solid solution treatment, Al₂Cu and Mg₂Si dissolved into the matrix and Cu was distributed uniformly in the matrix. However, Mg was still preferentially distributed near the boundaries of the Al particles and in the clusters of SiC. No change of the phases types in the composites was found, however, the extrusion resulted in uniformly distribution of the SiC particles and broke up the oxide shell of the initial Al particles, thus Cu and Mg were distributed homogeneously in the extruded composites after solid solution treatment.

By adjusting laser power and nozzle speed in laser cladding technology, crack–free titanium layer with even thickness and titanium mass percentage over 99%, was obtained on the substrate of low carbon steel without any intermediate layer when heat input was between 12—20 J/mm. The temperature field and the mechanical strain were simulated. Together with phase diagram and EDS, it was found that an interface zone, consisted of TiFe, (TiFe+β–Ti) eutectic compound and α–Ti, was formed between the titanium layer and the substrate. The interface zone is brittle and cracks occur in it. In titanium layer crack also occur if the mechanical strain exceeds the critical plasticity of metal. By reducing heat input, the mechanical strain decreases, thus a crack–free titanium layer with even thickness can be obtained.

The effect of interface energy anisotropy on the sideplate growth in Ti–6Al–4V is studied using 3D quantitative phase field method. The dynamic and thermodynamic data come from the DICTRA and Thermo–Calc databases, respectively. The results show that the interface anisotropy is an important factor controlling the shape of plates. Larger interface energy anisotropy results in wider plates and thicker residual β phase. Statistics of plate width, thickness and inter–platelet β phase thickness show that the evolutions of the width to thickness ratio of sideplate are different for systems with different interface energy anisotropy ratios. Solute concentrations are found inhomogeneous in the β phase near α/β interface (Al–poor and V–rich). The stronger the interface energy anisotropy is, the greater of the inhomogeneity. Higher temperatures result in slower growth, forming wider and thicker plates.

XRD and OM were used to study the phase constitution and solidified structure of the Ti–6Al–4V alloys prepared by laser multi–layer deposited pre–alloyed powder and blended elemental powder. It was found that the deposited layer obtained by using the pre–alloyed powder consists mainly of the epitaxial columnar grains, and the solidified structures change from the columnar grains to the equiaxed grains with increasing laser power. Meanwhile, the solidified structures of the deposited layer obtained by using the blended elemental powders change from large equiaxed grains to epitaxial columnar grains with increasing laser power from 1600 W to 2700 W. Laser scanning velocity has little effect on the morphology of the prior grains in the deposited layer obtained by using the blended elemental powders. The influence of mixing enthalpy on the structures of Ti–6Al–4V alloy was discussed also.

An 18Ni (C–250) maraging steel was successfully processed by equal–channel angular pressing (ECAP) for a single pass at room temperature. After ECAP deformation, the peak aging time was cut obviously and the peak strength of the steel was enhanced about 100 MPa. Microstructural observations showed that the martensite laths of 18Ni maraging steel were elongated to more narrow bands with a width of 100—200 nm after ECAP deformation, and the width of martensite lath was not affected by the subsequent aging treatment. ECAP deformation has significant influence on the size of rod–shaped δ–Ni3Mo precipitates. It was observed that the widths (diameters) of precipitates in specimens under treatments of solution+480℃, 4 h, solution+ECAP+480℃, 4 h and solution+ECAP+460 ℃, 4 h are 4.92, 12.33 and 3.54 nm, respectively. Additionally, a decomposition of the δ–Ni3Mo precipitates was accelerated after the peak aging time, resulting in a decrease in the strength.

High cycle fatigue (HCF) behavior of the second generation single crystal nickel–based superalloy DD98M without Re addition at 900 ℃ was investigated. The results indicate that HCF lifetime is reduced with increase of cyclic stress amplitude. Compared to smooth specimens, the fatigue lifetime and strength of notched specimens are decreased markedly. The fatigue strengths for smooth and notched specimens are 574 MPa and 360 MPa, respectively. Fracture observation by SEM shows that there exist many sites of crack initiation for notched specimens due to stress concentration of the notch, while for smooth specimens, crack generally initiates at pores and inclusions on the surface or subsurface. Deformed microstructures observed by TEM reveal that for smooth specimens, dislocation movement in the matrix is the main deformation mechanism and shearing γ' particles by dislocation pairs occurs occasionally under high stress level. In contrast, cutting γ' phases by partial dislocations, which formed stacking faults in γ', is the dominant deformation mechanism for notched HCF specimens.

The effects of rapid heating continuous annealing on microstructure and mechanical properties of ultra–high strength and low silicon TRIP steel containing phosphorus and vanadium were investigated. The results show that the yield and tensile strengths are increased with increasing intercritical annealing temperature during rapid continuous annealing. However, the intercritical annealing temperature can not increase blindly to ensure its excellent combined mechanical properties. When the heating rate is 80 ℃/s and intercritical annealing temperature is 880 ℃, the retained austenite not only contains fine blocky structure, but also a large amount of interlath retained austenite films. A great amount of V(C, N) precipitates exists within ferritic matrix, and the sizes of most of the precipates are in the range from 4 to 9 nm. The tested steel has excellent mechanical properties: R_m=1010MPa, R_P0.2=690MPa, δ=23.6%, n=0.27, r=1.17, the product of strength and ductility (R_m×δ) is 23836 MPa·%. If the intercritical annealing temperature is too high or too low, the comprehensive  mechanical properties will be deteriorated since the volume fraction of retained austenite reduces,  morphology changes and its size increase.

Use Cu–31Si alloy (31mol% Si) prepared by inductive melting metallurgical grade silicon as anode and molybdenum as cathode and reference electrode, the cathodic behavior of molten salt 81CaCl2–8.0 NaCl–8.5CaO–2.5Si (Mole fraction, %) at 1173 K was studied by means of cyclic voltammetry and chronopotentiometry, and the reduction steps of silicon from the molten salt were discussed. The electro–refining of silicon was performed in the two electrode system under the voltage of −0.2 V. SEM, EDS and inductively coupled plasma atomic emission spectrometry (ICPAES) technologies were used to analyze and characterize the morphology and composition of the deposited silicon. Polycrystalline silicon was obtained after the electro–refining. Main impurity in the metallurgical grade silicon are greatly decreased. Especially boron and phosphorous which are very harmful to solar cell grade silicon were greatly removed. The contents of boron and phosphorous are decreased from 42×10⁻⁶ and 25×10⁻⁶ to 4.5×10⁻⁶ and 8.2×10⁻⁶, respectively. The current efficiency of the electro–refining process is 84.4%.

The partition behavior of hafnium among different phases in FGH97 PM (powder metallurgy) superalloy and its effects on the precipitation behaviors of MC carbide and γ' phase were studied by means of 3DAP, SEM, TEM and physiochemical phase analysis. The results showed that element Hf mainly exists in γ' phase and MC carbide, which makes γ' composition transform to (Ni, Co)₃(Al, Ti, Nb, Hf), also makes MC transform to (Nb, Ti, Hf)C. With Hf addition increasing, the proportion of Hf in γ' maintains constant, but in MC carbide increases and in γ decreases, which means that partition ratio (R₁) between γ' phase and MC carbide is decreased, while partition ratio (R₂) between γ' phase and γ matrix is increased, the average partition ratio between γ' phase and MC carbide is about 1 :0.1, and the average partition ratio between γ' phase and γ matrix is about 1:0.05. Hf is helpful to the precipitations of γ' phase and MC carbide, the morphology and size of γ' phase are influenced more by Hf than these of MC carbide.

The surface hardness field, modificative layer microstructure and fatigue properties of carburized M50NiL steel after ordinary grinding and precision grinding, were studied using Vickers hardness tester, XRD, TEM, HRTEM and the rotating bending fatigue tester. The results showed that two grinding processes are different only on the amount of feed and surface roughness, but bring larger changes in the surface hardness field, modificative layer microstructure and fatigue properties. Two kinds of grinding have different effects on the hardness depth, the impact depth of precision grinding is smaller; There was more austenite on ordinary grinding surface, and the surface layer showed a clear modificative layer of austenitic"effective grain"; precision grinding surface modificative layer is very small deformation nano–martensite, but also shows a clear"effective grain"phenomenon;effective grainno obvious interface; "effective grain"turning phenomenon is apparent, adjacent "effective grain"rotation angle is up to 14^?, while, there are slight turning phenomenon within the"effective grain"; rotating bending fatigue life of precision grinding increases by about 13 times of ordinary grinding sample.

According to the formula of grain growth under isothermal condition, the kinetics equation of ferritic grain growth in heat affected zone (HAZ) was obtained, which was combined with the calculated thermal cycles to predict the grain growth in HAZ of TCS stainless steel under the new–type welding procedure–hybrid welding. The grain sizes in HAZ of TCS stainless steel have been calculated for three welding conditions. Simulation results are validated by the average grain sizes measured on the metallographic images of the welding joint of TCS stainless steel. Preliminary discussion has been made on correlation of the grain growth with the thermal cycles and the effect of local variation in thermal cycles on the grain growth.

2024 aluminum alloy sheets with three different thicknesses were shocked by means of a single laser shock processing. Static and dynamic strain signals from the strain gauges on the back of the target were measured by STSS–1 stress test module. Residual stresses of target surfaces were measured by XRD. The loading model by the laser shock waves in 2024 aluminium alloy sheets was established, the stress wave propagations and stress wave structures inside the targets were described, and the reasons of generating residual tensile stress in the impact areas were explained. The results indicate that laser shock waves reflected and transmitted have different properties and intensities at the different places of target surfaces. When the laser power density is far beyond the best power density range of 2024 aluminum alloy and the target material is thin enough, the tensile residual stresses are generated.

The microstructures and room temperature mechanical properties of metal–mold– casting aluminum alloy Al–6.3Zn–2.8Mg–1.8Cu were studied. It was found that the microstructure of the as–cast experimental alloy consists of near equiaxed α(Al) matrix, α(Al)+η(MgZn₂) eutectic and little Al₇Cu₂Fe particle phase. The phase constitution of the quenched experimental alloy was changed, the η phase was dissolved into α(Al) matrix and tended to disappear, however a new phase, S(Al₂CuMg), appeared, which still mainly distributed along the α(Al) grain boundary. The optimum single–aging process parameters were determined by investigating age hardening response of the experimental alloy. It was found that the double–aging process could make the tensile strength of the experimental alloy increase from 480 MPa to 490 MPa, and the elongation from 0.2% to 2.2%,comparing with the single–aging process.

Due to the excellent high temperature mechanical properties, Al₂O₃/YAG/ZrO₂ ternary eutectic in situ composite is considered to be a promising candidate for the material, replacement for nickel based superalloy, of new generation aero space engine turbine blade. The directionally solidified Al₂O₃/YAG/ZrO₂ hypereutectic ceramics are prepared with recently developed laser floating zone melting (LFZM) apparatus. Full eutectic lamellar microstructure, free of primary phase, was obtained with hypereutectic composition. The formation of solid/liquid interface morphology was analyzed in detail. The microstructure texture tendency was explained by combination with interface morphology. The experimental result indicates that, just as the prediction of JH model, average spacing of hypereutectic (λav) agrees with the inverse–square–root dependence on solidification rate (V ) according to λ_avV ^0.5=14.7 μm^1.5·s^−0.5. In lower solidification rate, the lamellar spacing of hypereutectic is higher than that of eutectic composition, but the situation reverses in higher rate. The main reason of such phenomenon is that the addition of ZrO₂ effects the thermal and solute transformation in the melt. The influence of transformation condition on lamellar spacing was analyzed synthetically by using classical irregular growth model. The formation mechanism of banded microstructure, often observed in laser zone melted solidification processing, was also discussed.

The effects of hard particles with different shapes, volume fractions and sizes on two–phase grain growth have been systematically investigated by phase–field method. The results showed that most of the spherical hard particles located at the intersection of tricrystal boundary, while flaky hard particles distributed along the grain boundary. Particles of different shapes have not obvious effect on the α phase grain growth, and the effect of hard particles with different shapes on the β phase grain growth depends on the number of particles. The flaky particles have stronger pinning effect on the β phase grain growth than the spherical particles when hard particles reach enough number. The pinning effect of the hard particles is enhanced when the volume fraction increased or the size of hard particles reduced. The greater the volume fraction or the smaller the size of hard particles is, the smaller the grains’size is.

Directional solidification (DS) process of Ti–43Al–3Si alloys in an optical floating zone furnace has been studied. The Φ9 mm polycrystalline rods with appropriate microstructure were cut from Φ70 mm cast ingot and used as seeds. At a growth rate of 5 mm/h, the DS ingot with lamellar structure parallel to longitudinal axis was obtained. The results of OM show that in the L+α+β three–phase region, the central α phase was successfully seeding by the polycrystalline rods and gradually develops into a dominant microstructure under a bent solid–liquid interface. The selection of polycrystalline seed, principle of three–phase region and bent solid–liquid interface directional solidification were discussed in detail.

A modified Miracle model based on packing different atoms on the first shell of solute–centered cluster is advanced to predict the best glass–former in some high content (pseudo–) ternary systems such as Ti–Ni–Al etc. The calculated results not only for the best ribbon metallic glass–formers in Ti–Ni–Al, Ti–Ni–Sn, but also for the best bulk metallic glass–formers in some other systems correspond to the experimental results very well, indicating the validity of this model.

The depth profile measured by secondary ion mass spectroscopy is influenced by factors such as the atomic mixing caused by ion injection, the crater edge, the crystallographic orientation of grains and the surface roughness etc., resulting in the deviation of the measured profile from the real distribution of the solute atoms. A depth profile measured before diffusion annealing or the "zero profile"is a comprehensive characterization of all the factors that influence the depth profile after annealing. In the present study, a mathematic method using Fourier serials to effectively deconvolute the real profile from the measured profile and"zero profile"is proposed. And the effects of "zero profile" on the diffusion properties of Zn in a coarse grained Cu and a nanostructured Cu produced by dynamic plastic deformation (DPD) at liquid nitrogen temperature (LNT) are analyzed with the above method.

1.2 mm thickness sheets of ultralight Mg–11Li–3Zn alloy with a density of 1.43 g/cm³ was obtained by casting and rolling, the elongation to failure is 200% at 573K with 1.67×10⁻² s⁻¹ tensile rate, which indicates high strain rate quasi–superplasticity. Significant dynamic recrystallization and grain refinement occur at 573 K and 1.67×10⁻² s⁻¹ under which the grain size turns from initial 27 μm into 9 μm, the stress exponent is 4.4 and the activation energy for flow is 112.6 kJ/mol. It is considered that the deformation mechanism of Mg–11Li–3Zn alloy at 573 K and 1.67×10⁻² s⁻¹ is dislocation climb controlled by lattice diffusion.