In order to study the early stages of plastic deformation with initial defect under the action of an indenter, the nanoindentation processes of the single crystal aluminum thin film were simulated using the quasicontinuum method. The load vs displacement response curves and strain energy vs displacement curves of the single crystal aluminum thin film with initial defect and defect--free were presented, respectively. The nanoindentation processes under influences of the initial defect were investigated about dislocation nucleation, dislocation emission, Peierls stress and load necessary for dislocation emission. The results demonstrate that the load vs displacement response curves experience many times abrupt drops with the emission of dislocations beneath the indenter. The initial defect is found to be insignificant on nucleation and emission of the 1^st and 3^rd dislocation dipoles, but has a distinct effect on the 2^nd dislocation dipole. The nucleation and emission of the 2^nd dislocation dipole is postponed obviously because of the effect of initial defect, and then crack propagation is accompanied. The strain energy of single crystal aluminum thin film and Peierls stress of dislocation dipole beneath the indenter increase with deformation processes due to the severe lattice distortion in the thin film. Before the cleavage occurs, the load necessary for the 2^nd dislocation dipole nucleation and emission increases in nanoindentation with initial defect, on the contrary, it decreases after the cleavage occurred. The nanohardness and Peierls stress in this simulation show a good agreement with relevant theoretical and experimental results.

The nanoscrath process of nickel nanofilm and plastic deformation mechanisms in the nanofilm are investigated by using molecular dynamics simulation. The results reveal that the stacking faults end at the grain boundaries as well as prismatic dislocation loops, leading to that plastic deformation on the grain boundary keeps in the film rather than transmiting downward the substrate. For thinner films, stacking faults are preferred in the scratch process, which increase storage capacity of plastic deformation in the film, and further inhibit the stick–slip amplitude in the friction oscillation process. For thicker films, dislocation loops, which glide along slip plane downward to the grain boundary, dominate over the stacking faults, and finally dissipate on the grain boundaries. Since the intergrain stacking faults are inactive in thicker films, the stick–slip phenomenon is similar to that in single crystal. The evolutions of subsurface microstructures in the nanoscratch process result from the dislocation structures emitted in nanofilms with different thickness.

The quasi–static and dynamic compressive mechanical properties of cold–rolled and annealed Cu sheets were investigated by means of Instron apparatus and Split–Hopkinson pressure bar (SHPB) technology, respectively. Cylindrical specimens of textured Cu sheets, which were cut with the
cylinder axes along the rolling direction (RD), transverse direction (TD) and normal direction (ND), were compressed at strain rates in the range of 10⁻³ to 10³ s⁻¹. The compressive stress-strain curves show all that the flow stresses for both cold rolled and annealed Cu sheets increase with the increase of strain rate and the obvious effect of strain rate hardening has been observed. The quasi–static and dynamic compressive mechanical properties of the cold rolled Cu sheet exhibit pronounced anisotropy, both the yield strength and flow stresses at the low deformation degree for the TD direction are the maximum, while those for the RD direction are the minimum. The properties of annealed Cu sheet are isotropic. Taking into account of possible mechanism for quasi–static and dynamic plastic deformation, the mechanical anisotropy of textured Cu sheets could be explained qualitatively by Taylor model based on the microscopic crystal plasticity theory.

The microstructure evolution of hypereutectoid steels during warm deformation was investigated by uniaxial hot compression simulation experiment and by means of SEM, TEM and EBSD, especially for the formation of equiaxial ferrite grains and the effects of Al on the formation of equiaxial ferrite grains. The results indicate that the microstructure evolution of hypereutectoid steel during warm deformation involves the spheroidization of lamellar cementite, the equiaxial process of ferrite and the re–precipitation of cementite particles. At the beginning of warm deformation, lots of dislocations are introduced into ferrite, and subgrain boundaries are formed by dynamic recovery of ferrite. With the strain increasing, subgrains rotate due to the pinning effect of cementite particles, leading to the formation of high angle grain boundaries, i.e., the formation of equiaxial ferrite grains is actualized by the dynamic continuous recrystallization of ferrite. By the addition of Al, the coarsening of cementite is hindered, the sizes of cementite particles and ferrite grains are refined and the fraction of high angle grain boundary is increased.

The effects of Al on the spheroidization of cementite and the formation of ultrafine (α+θ) microstructure of hypereutectoid steel during isothermal spheroidizing and warm deformation were investigated by uniaxial hot compression simulation experiment. The results indicate that during isothermal spheroidizing, the fine grained cementite particles and ferrite are obtained by addition of Al. Ultrafine (α+θ) microduplex microstructures can be formed by warm deformation in a very short time. During warm deformation, the diffusion of carbon and iron atoms are impeded with the addition of Al, the spheroidization of lamellar cementite and the coarsening of cementite particles are retarded. And the re–precipitation of cementite particles in ferrite matrix is also restricted, resulting in a more ultrafine (α+θ) microduplex microstructure.

The hot corrosion resistance of a new directional solidification (DS) Ni–based super-alloy DZ68 was studied and compared with K438 alloy. The results indicate that the microstructure of DZ68 alloy is more uniform than K438 alloy after heat treatment. There are small size carbides in the microstructure of DZ68 alloy after heat treatment, but there are big size carbides and a lot (γ+γ') eutectic in the microstructure of K438 alloy. The hot corrosion of DZ68 alloy is uniform, and the corrosion products are mainly (Ni, Co)Cr₂O₄ and Al₂O₃. More (Ni, Co)Cr₂O₄ exists in outer corrosion layer and more Al₂O₃ exists in inner corrosion layer. For the K438 alloy the hot corrosion is not uniform, NiO is the mainly corrosion product in outer corrosion layer and CrS is the main corrosion product in inner corrosion layer. Moreover, the segregation of Ti can induce segregation of other elements in the two alloys, which leads to a severe local corrosion of alloys. Under the same expermental condition, the corrosion resistance of DZ68 alloy is a little better than that of K38 alloy.

Effects of B on the microstructure and hydrogen resistance performance in an Fe–Ni base alloy were investigated by means of optical microscopy, scanning electron microscopy, thermal hydrogen charging experiments and tensile tests. The results show that abundant η(Ni₃Ti) phases precipitate at grain boundaries (GBs) in the alloy without boron (FN) after aging treatment, while only a few carbides precipitate at GBs in the alloy with boron (FNB). Tensile tests indicate that the FNB exhibites not only higher ductility but also lower hydrogen–induced ductility loss than those for FN alloy. Fracture observations show that the brittle intergranular fracture is the main feature of peak aging and over aging FN alloy and quite a few secondary cracks can be observed on fracture surface of the hydrogen charged samples due to the precipitation of η phase at GBs. However, the intragranular
fracture is dominant feature for the FNB alloy whether hydrogen charging or not.

The thermally activated deformation and dynamic strain aging (DSA) of Zr–4 were investigated by stress relaxation experiments in a broad temperature range. It is found that in the process of stress relaxation, the plastic deformation rate of the alloy decreases with the relaxation
time, and this rate and the stress reduction ratio at the end of relaxation exhibit a minimum value at about 623 K. The activation volume associated with dislocation motion is found from the relationship between the stress and relaxation time. A noticeable maximum value appears around 623 K when the activation volume plotted against the temperature, which suggests that at this temperature, DSA is most pronounced. The strain ependence of the activation volume is analyzed. The rate controlling deformation mechanism is identified as the overcoming of solute atoms by dislocations, and the dislocation density is found to have an influence on DSA.

The polarity growth of intermetallic compound (IMC) at the interface between eutectic SnPb BGA solder joints and Ni(P) finishes was investigated and the mechanism of microstructural evaluation was explained by the migration of atoms in interconnects. Ni₃Sn₄ IMC layer of 2 μm in thickness was formed during the soldering reaction and the subsequent annealing at 120 ℃ can not induce the visible growth of IMC. The IMC layer shows abnormal growth at the anode interface, while the growth at the cathode interface is restrained. Finally, the upper–side and lower–side interfaces of
the same solder joints show polarity effect on the growth of IMC. The polarity effect is related with the flux of atoms in interconnects. The direction of electron flow is consistent with the flux of Sn atoms, while opposite to the flux of Ni atoms. The flux of atoms induced the abnormal growth of IMC at the
anode interface but restrained the growth at cathode interface.

Although the residual distortion of 6056 Al alloy sheet after friction stir welding (FSW) is smaller than that after fusion welding, it is still a significant defect for the assembly and application of welded structure. In order to investigate and predict the residual distortion of Al alloy sheet after FSW, a 3D thermo–mechanical model was established based on experimental conditions to simulate the FSW process. In the model, heat input was computed based on the torque data measured during experiment, and heat transfer between welded sheet and fixtures was simplified in the way of convection, and the properties of 6056 Al alloy were considered as temperature function, and tool loads were taken into account during the mechanical analysis. The simulation results show that the distribution of longitudinal residual stress along the width of sheet is asymmetrical, and the residual distortion corresponds well with experimental results both in distortion pattern and deformation values on the whole sheet.

Dimensional analysis was constructed to derive the dimensionless functions of a spherical indenter with 1 mm in diameter. The function can be used to extract the yield strength and strain hardening exponent of metal materials by means of finite element analysis. The fitting functions used to analyze materials yield strength and strain hardening exponent within the yield strains ranging from 0.00769 to 0.04 were obtained by numerical simulation. It has been validated that the prediction accuracy is enhanced and the average errors of the yield strength and strain hardening exponent are 1.6% and 12.6%, respectively.

The effects of grain boundary characters on the morphology evolution of the intergranular carbide in Ni--based alloy 690 with high proportional
low ∑coincidence site lattice (CSL) boundaries aged at 715 ℃ for 2---200 h were investigated by SEM. The results show that the sizes of
intergranular carbides decrease with ∑value decreasing, and only fine carbides at coherent ∑3 are almost not changed after aging for 200 h. Plate--like carbides precipitated near both incoherent ∑3 and ∑9 boundaries, and the carbide plates grow bigger with the aging time prolonging, in which the former precipitated near both sides of incoherent ∑3 boundary and the latter precipitated near only one side of ∑9 boundary. The morphology of carbide precipitated at ∑27 boundary is similar to that precipitated at the general high angle grain boundary, and no plate--like carbides are observed near these boundaries.

Large sized ErSn₃ particles precipitated in the Sn–3.8Ag–0.7Cu–1.0Er solder alloy are oxidized when exposed in air, and it was found that Sn whiskers can rapidly grow on the oxidized ErSn₃. During aging at room temperature, a few rod–like Sn whiskers were observed and their diameter
could be gradually changed. During aging at 150 ℃, a great number of needle–like Sn whiskers were observed and their diameter could be also changed step by step. A model, in whicthe volume stain energy is not a constant during oxidation of ErSn₃, was suggested to explain the observed results.

The corrosion behavior and corrosion kinetics of FGH95 alloy at different temperatures were investigated by TGA, XRD, SEM and EDS. The results show that FGH95 alloy has good hot corrosion resistance characteristics at 650 ℃, and its corrosion kinetic curve obeys a parabolic rule. When the temperatures increase up to 700 and 750℃, the hot corrosion resistance of FGH95 alloy decreases and corrosion is serious. XRD, SEM and EDS indicate that the oxidized layer is mainly composed of NiO, Ni₃S₂ and Cr₂O₃, and there exists a little amount of NiCr₂O₄ and NaCl at 700 and 750 ℃, respectively.

Molecular dynamics (MD) with embedded atom method (EAM) was used for describing the variations of adsorption, sputtering and vacancy on surface with energy of incident atom Ti.The results show that a sputtering threshold energy of about 40—50 eV exists in the deposited process, and the incident atom with energy below the threshold value can be thought as deposited atom. Otherwise,the sputtering yield increases linearly with the increase of incident energy. Both distributions of adsorption and sputtering atoms present a 6–rotational symmetry. Adatoms mostly come from surface atoms of the substrate when incident energy is above threshold value, and the probability of incident atoms becoming adatoms is very little. Vacancies distribute mainly on the 1st layer and their amount in the sub–layer increases with the increase of incident energy which is above threshold value.

The electronic structures and properties of Pb_0.5Sr_0.5TiO₃ (PST) were calculated by the plane wave ultra–soft pseudo–potential and virtual crystal approximate (VCA) technologies based upon the density function theory (DFT) within the general gradient approximation. The changed trend of the total energy of PST solid solution was analyzed, and the equilibrium configuration of A–site cations (Pb and Sr) in the ferroelectric phase was determined. The calculated results revealed that the energy of PST appeared minimum when the off–center displacement of Ti atom was up to
0.012 nm along (001) direction. The strong hybridization between O 2p and Ti 3d and part hybridizations between O—Pb and O—Sr showed an increase in the distortion of TiO6 octahedron and a reduce in the system total energy, which led to the formation of ferroelectric domains.

Phase transformation during preparation of Y_2−x−yGd_xEu_yO₃  (x + y ≤2) nanoparticles by citric acid chelating and influence of pH value on the powder morphology were studied by FTIR, XRD and SEM. The behavior of solid solution was analyzed through calculation of lattice parameters and unit cell volume of Y_2−x−yGd_xEu_yO₃ and its luminescence property was obtained. The results show that the appropriate condition to prepare cubic Y_2−x−yGd_xEu_yO₃  powder is that the pH value less than 3, calcining at 900℃ for 2 h. Y_2−x−yGd_xEu_yO₃  powders with spherical morphology and size of 90 nm can be prepared under the condition of pH=1 and adding a little amount of glycol (5%, volume fraction). Luminescence properties of the powders are affected by the ratio of Y, Gd and the content of Eu. The luminous intensity reaches the maximum value when the powder composition is Y0.2Gd1.65Eu0.15O3. Concentration quenching occurs when y is above 0.15 and then the emission intensity decreases.

A large sized La₆₂Al_15.7(Cu, Ni)_22.3 amorphous alloy was produced by spray deposition, and its compressive deformation behavior in supercooled region was investigated. It is found that both the strain rate and test temperature significantly affect the stress–strain behavior of the amorphous alloy in the supercooled liquid region. The deformation behavior is characterized by a transformation from unsteady–state flow to steady–state flow with the decrease of strain rate or increase of heating temperature in the supercooled region. After hot extrusion at 443 K, the alloy is still amorphous and its density (5.924 g/cm³) is 96.6% of the suction-cast amorphous alloy with the same component (6.134 g/cm³) when the reduction ratio, strain rate and heating temperature are adopted as 6.25, 5×10⁻³ s⁻¹ and 443 K, respectively.

Crystallization processes and non–isothermal crystallization kinetics of Nd₆Fe₇₂B₂₂ and Nd₆Fe₆₈Ti₄B₁₇C₅ amorphous thick ribbons rapidly quenched at a roller running rate of 12 m/s were investigated by means of DSC, XRD, Kempen model and Kissinger equation, respectively.
Two thick ribbons show different crystallization processes and kinetic mechanisms. The crystallization processes of Nd₆Fe₇₂B₂₂ and Nd₆Fe₆₈Ti₄B₁₇C₅ alloys can be discribed as: amorphous phase (AP)→ Nd₂Fe₂₃B₃→Nd₂Fe₁₄B+ α--Fe +Fe₃B→Nd₂Fe₁₄B+α--Fe+Fe₃B+NdFe₄B₄, and AP→Nd₂(Fe, Ti)₁₄(B, C)+α--Fe + Fe₃B, respectively. Different from polymorphic crystallization controlled by interface for Nd₆Fe₇₂B₂₂ alloy, the crystallization of Nd₆Fe₆₈Ti₄B₁₇C₅ is eutectoidic and the nucleus growth is controlled by diffusion.

The glass forming ability (GFA) of a newly developed Zr_50.7Cu₂₈Ni₉Al_12.3 alloy can be improved by minor addition of Gd element, for example, the amorphous alloy Zr_50.7Cu₂₈Ni₉Al_12.3 has a critical diameter of 14 mm, but the alloy added by 1%Gd (atomic fraction), (Zr_50.7Cu₂₈Ni₉Al_12.3)₉₉Gd₁,
has 16 mm critical diameter. However, the Gd addition decreases the fracture strength and plastic strain under compressive condition. Meanwhile, with Gd addition increasing, the fracture mode transforms from pure shear to shear with hysterical failure. A combination of vein pattern and nanoscale corrugations can be clearly observed on the fracture surfaces of the alloys with Gd addition.

[(Fe_1-xCo_x)_71.2B₂₄Y_4.8]₉₆Nb₄ (x=0, 0.1, 0.2, 0.3 and 0.4) alloy rods with 2—5 mm in diameter were prepared using commercial materials and suction casting method. XRD results show that the substitution of an appropriate amount of Co for Fe can improve effectively the glass forming ability and extend considerably the composition scope for glassy formation. DTA curves indicate that all the alloys with different Co contents exhibit a high glass transition temperature (T_g≥850 K) and wide supercooled liquid region (ΔT_x≥97 K). It is also observed that Co substitution for Fe enhances significantly the soft magnetic properties. For the [(Fe_0.9Co_0.1)_71.2B₂₄Y_4.8]₉₆Nb₄ bulk metallic glass, the saturation magnetization (M_s) has a maximum value of 26.6 kA/m, while the coercivity (H_c) is only 59 A/m. In addition, the Curie temperatures of the tested alloys increase continuously with the increase of Co content, and reaches the highest value of 577 K when x=0.4, which is about 100 K higher than that of the base alloy without Co.

On the basis of the theoretical model of soft reduction gradient, the soft reduction gradients for continuous casting bloom under different casting speeds were investigated. The results show that the reduction gradient of bloom is the biggest at the inlet of soft reduction zone, and decreases linearly along the strand. The value of bloom reduction gradient is much lower than that of slab at the outlet of soft reduction zone, and little different from that of slab at the inlet of soft reduction zone. As the casting speed increases by 0.1 m/min, the average reduction gradient of bloom decreases by 0.04 mm/m. It seems that the casting speed has no effect on the range of reduction rate which changes linearly from 0.13 to 0.04 mm/min. And the average reduction rate of bloom, which is independent of casting speed and keeps the value of 0.088 mm/min, is much lower than that of slab.