The structure, composition range and phase equilibrium of the ternary compound T1 with low Nd content in the Mg-Zn-Nd alloys have been investigated by scanning electron microscopy, electron probe microanalysis, X-ray diffraction and electron diffraction. It has been shown that the ternary compound T1 with the hcp structure, whose structure parameters are a=b=1.5nm, c=0.87nm, exists in the Mg-Zn-Nd alloys with low Nd content. The composition range of the T1 phase is 27.0~33.4at%Mg, 60.0~66.4at%Zn and 6.1~7.4at%Nd. At the temperature range of 300~400℃, there exists (Mg)+T1 two-phase field; and the Zn content in the (Mg) which is in two- phase equilibrium with T1 increases with the temperature. Three-phase field T1+(Mg)+MgZn exists at 300℃, T1+MgZn+L exists at 350℃, and T1+Mg2Zn3+L exists at 400℃ in the Mg-Zn-Nd system.

The surface recrystallization in a Ni3Al base single crystal alloy IC6SX which is developed for advanced aeroengine turbine blades and vanes has been studied. The specimens were cold worked by grit blasting and then heat treated in the temperature range of 800-1260℃ for 1h to 10h. The experiment results showed that initial recrystallization nucleation temperature was about 1000℃ and the primal recrystallization completing temperature was between 1200-1210℃.It has been found that the recrystallization grain size increased significantly with increasing temperature. However, the thickness of recrystallization layer almost kept to be 10 μm in the temperature range of 1200-1240℃ for 1h, and increased fast with increasing temperature above 1240℃ i.e., the thickness of recrystallization layer was ～23μm after 1260℃/10h. The results indicated that different from the recrystallization behavior in most common Ni-base superalloys, the recrystallization grains in the interdendritic region grew faster than in the dendritic core. It was observed that a cellular transformation formed in the interface between recrystallization grain and the dendritic core.

Magnesium sheets produced by different process were studied in this paper. The microstructure and mechanical properties of the alloys were analyzed by optical microscope (OM)、scanning electron microscope (SEM)、transmission electron microscope (TEM) 、digital microhardness tester and electron test equipment. The conventional casting ingot and twin rolling casting strip were all can be hot rolled at certain temperature and get magnesium sheets with 1mm thickness had refined and uniform deformation microstructure, the alloys were recrystallized after heat treatment and got equiaxed structure. The alloys had good mechanical properties after hot rolling, the strength and the elongation of twin roll casting alloy were evident higher than those of the conventional casting alloy. The tensile strength, yield strength and elongation of twin roll casting alloy and conventional casting alloy after hot rolling and 350℃×10min annealing were 334.4MPa, 229.3MPa, 23.8%, and 270.8MPa, 174.4MPa, 10.8%, respectively. The fracture surface of the alloys all took on ductile fracture contains lacerated ridge and ductile sockets, but the twin roll casting alloy had more evidence and smaller ductile sockets, this because the grain size of twin roll casting alloy was finer than that of conventioanal casting alloy.

Hydrogen embrittlement susceptibility of 40CrNi3MoV steels with Si contents of 0.25% and 1.16% and the strength level of 1500 MPa was investigated by means of slow strain rate tests. The reduction of notch tensile strength after introduction of hydrogen was used to characterize hydrogen embrittlement susceptibility and compact specimens were used to investigate hydrogen-induced crack propagation. Results show that the higher Si content 40CrNi3MoV steel was less susceptible to hydrogen embrittlement than the lower Si content 40CrNi3MoV steel with the same strength level of 1500 MPa, resulting from more and finer carbides which may act as hydrogen trapping sites and prevent hydrogen from diffusing to fracture process zone.

The microstructures and mechanical properties ofЭП866 martensite heat-resistant steel submitted to equal channel angular pressing (ECAP) for one pass and subsequent heat treatment were investigated. It was hound that most of the lath martensite has been broken, and the nano-precipitant distributed more uniformly after ECAP deformation. By annealing at 680℃ for 2h, the dislocation density decreased and a great deal of equiaxed subgrains with sizes of several hundred of nanometers were produced, which could be attributed to the dislocation recovery and recrystallization. The yield strength of the ECAPed sample increased significantly, but its ductility decreased a lot. After subsequent annealing treatment, the ductility of the ECAP steel can be improved to the level of initial state. Both the strength and static toughness of the steel after ECAP deformation and subsequent heat treatment can be increased simultaneously compared with those of initial state.

The degassing effect and the grain refinement of Al-Si alloy with power ultrasound were studied. The value of porosity volume of Al-Si alloy decreases obviously when the treated time is 60s. The grains are fine and globular when the solidification of Al-Si alloy was treated by power ultrasound and the grains are fine but not globular at isothermal temperature in the mushy zone with ultrasonic vibrations. The results imply that the expansion and collapse of cavities which results in the formation of nuclei plays the dominant important role in the formation of fine and globular grains.

In order to investigate the size dependence of the plastic deformation properties for metal foil, uniaxial tensile tests of brass foil specimens with different thicknesses and grain sizes are performed at room temperature. The results show that with the decreasing thickness or grain size, the yield strength of the specimen increases. The influence of the grain size on the yield strength meets the Hall-Petch relation of the grain size strengthening. The increase in the yield strength of the thinner specimen is expected to attribute to the decrease of grain size. In addition, the ratio of thickness to average grain size can not express the size effect of the yield strength if the thickness is less than 100µm.

Force and deformation of the specimen during ring hoop tension test were analyzed. Distribution of radial normal force and hoop tension force were discussed and equations derived. FEM analysis and experiments were carried out to verify the theoretical analysis. Results show that the FEM and experimental results agreed well with the distribution of hoop tension fore. The hoop tension force is axisymmetrical about the tension direction and increase from the top position to both sides. The distribution of hoop tension force is even with small friction coefficient, but will increase rapidly from top to side positions, which subsequently result in necking and fracture near the edge of gauge section.

Mg97Y2X1（at%,X= Zn,Ni,Ag）alloys were prepared by induction melting method and characteristic long period stacking structures(LPS) formed in these alloys studied by transmission electron microscopy and scanning electron microscopy. The results show that the LPS in the as-solidified Mg97Y2Zn1 can be described as a structure with a 6-layer stacking period, which is different from the typical LPS of the 6H type in a hcp structure. The existence of LPS in the Mg-Y-Ni system has been found for the first time. The lattice distortion in LPS structures occurs more often in the Mg-Y-Ni system than in the Mg-Y-Zn system. In contrast, no LPS structure is found to be formed in the Mg-Y-Ag sysyem. On the basis of experimental results, the factors affecting the formation of LPS structures in Mg97Y2X1 alloys are also discussed.

The mechanical behaviors at elevated temperatures of aluminum alloys produced by squeeze casting process were studied using the physical simulation system Gleeble-1500D. A series of true stress-strain curves under temperatures ranging from 300℃ to 500℃ and strain rates ranging from 0.001s-1 to 0.1s-1 were obtained for the materials produced under different squeeze pressures (25MPa, 50MPa and 75MPa). Based on the experimental results, an elastic-viscoplastic constitutive model for describing the stress-strain relationship before and in the steady flow state was developed, and the mathematic expressions of several key model parameters were given. It is shown that the predictions of the model are in good agreement with the experimental data.

Multilayered Co/Pd nanostructure films are deposited on monocrystalline silicon(111) by using double-bath method and the technological conditions are determined. The mechanism of the growth kinetics for Co and Pd layers have been studied ,It is showed that the growth kinetics for Co and Pd are consistent with progressive nucleation.The mass change of layers are exactly measured by EQCM . XRD results suggest that the multilayer have good crystal lattice，and alloy-intermediate of Co and Pd are also found .In addition，hysteresis loops are measured by PPMS at room temperature .The result showed that : with decrease of Co thickness ,coercive force was increased and which up to 1130 Oe.

It has been reported that magneto-vibration is a key factor to cause residual stress reduction in steel during the process of magnetic treatment. In this paper the relationship between magneto-vibration and residual stress reduction caused by magnetic treatment in steel is studied. From the experimental results it shows that the existence of residual stress in steel can have some effect on the magnetostriction behavior, and further on the magneto-vibration behavior. When there exists residual stress in steel specimen, the value and the range of the magneto-vibration are different from those without residual stress. And with the development of magneto-vibration its value and range move to those without residual stress gradually. On the other hand the residual stress in steel specimen can be reduced after magneto-vibration. Therefore it can be concluded that when there exists residual stress in steel the magneto-vibration and residual stress influence each other so that the magneto-vibration with residual stress has a non-linear characteristic.

Directionally solidified Al2O3/Y3Al5O12 (YAG) eutectic in situ composite was prepared by the laser zone remelting technique. The eutectic morphology, phase composition, interface structure, microstructure evolution and phase precipitation rule were analyzed by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), energy disperse spectroscopy (EDS) and transmission electron microscopy (TEM). The irregular microstructure morphology was quantitatively characterized by fractal dimension. Further more, the irregular eutectic growth mechanism of the oxide eutectic was detailedly discussed. The results show that the directionally solidified Al2O3/YAG eutectic in situ composite only consists of homogeneously distributed Al2O3 and YAG phases with well matched interfaces. The two phases interweave each other and coupledly grow, showing a “Chinese script” structure. The YAG phase is the primary phase during solidification. The eutectic spacing is highly refined with increasing the laser scanning rate and the minimal spacing is down to 0.2um. At low laser scanning rate, the eutectic tends to show typical lamellar irregular eutectic structure and has evident fractal characteristic, whereas, when the laser scanning rate reaches a high value of 2000um/s, the cellular and dendritic structures appear and the fractal characteristic is weaken. The faceted/faceted eutectic growth derived from the large kinetic undercooling of laser rapid solidification and high entropies of fusion of eutectic phases is the most primary factor to determine the formation of the complexly irregular eutectic morphology.

FeS/SiC composite coatings have been successfully produced by plasma spray technique. SiC particles with nano-scale are uniformly distributed in FeS matrix. There is a good bond between the coatings and 40Cr steel substrate. The tribological properties of FeS coating and FeS/SiC composite coatings have been investigated. The results show that FeS/SiC composite coatings have good antifriction and wear resistance properties. The friction coefficients of the composite coatings, mixed with nano SiC particles in weight fraction 0.2 and 0.3, are almost same as that of FeS coating under dry sliding, but the wear volume of them is remarkably decreased over the range of an order of magnitude. In oil lubrication, the friction coefficient of FeS/SiC composite coatings is smaller than that of FeS coating. So the composite coatings have superior antifriction property in the case.

The liquid structuer of two molten lead-free solder alloys, Sn-0.7Cu and Sn-2Cu (wt.%), were studied at 260, 330 and 400篊 by using high temperature X-ray diffractometor. Only short range order (SRO) structure was detected in molten Sn-0.7Cu solder under all temperature. A pre-peak was found in the low Q part of the structure factor S(Q) of Sn-2Cu tested under 260篊, implying that there exists not only SRO structure but also medium range order (MRO) structure in molten Sn-2Cu solder. The appearance of pre-peak is related to the existence of Cu6Sn5-phase-like MRO clusters in molten solder. But the amount of Cu-Sn clusters decreased sharply with increasing temperature, and the pre-peak disappeared finally at 400篊 indicating that the temperature is high enough to destroy the bond in Cu-Sn correlations. The correlation raduis rc and the coordination number Nmin of the two liquid solders were obtained by calculation, and then the changing trend of the two parameters with temperature was set out. The result of Gaussian decomposition of the radial distribution function (RDF) shows that the size of Cu-Sn correlations in molten Sn-Cu solders increases with increasing Cu content.

The effect of Bi on the shear strength for Sn-3Ag-0.5Cu-xBi(x=0,1,3)/Cu solders joints has been studied after being aged at 140℃ and 195℃. The results indicate that fracture type changes from ductile fracture to brittle fracture with the increasing of IMC. Shear strength for Sn3Ag0.5Cu solder joints changes slightly when aged at lower temperature, but increases with the prolonging of the aging time and sharply drop at final by adding of Bi. When aged at higher temperature, shear strength for each kind solder joint decreases with the prolonging of aging time. Although the shear strength is relatively higher by adding Bi, the difference is small. It is seems that Bi can improve the shear strength by strengthening solder and decreasing the growth of IMC.

To develop the volumetric heat source mode for laser +GMAW Hybrid welding, four new kinds of distribution functions of volumetric heat sources are proposed after considering the geometry characteristic of laser deep-penetration welds and analyzing the action features of heat source in laser welding. Through numerical analysis of temperature profiles in laser welding, the geometry and dimension of weld cross sections in laser welding are obtained under the conditions corresponding to the four kinds of distribution functions of volumetric heat sources. After comparing the predicted results to the experimental measurements, it is found that the proposed four kinds of volumetric heat source modes are appropriate and adaptive in characterizing the effect of laser thermal action on weld formation, which lay foundation for developing heat source modes in laser +GMAW Hybrid welding.

Due to Magnesium alloys with hcp crystal structure, we established the phase field model of dendritic growth in two dimensions. Using the model coupled with heat noise, we simulated the process of dendritic growth of Magnesium alloys. From simulation results, some phenomena of dendritic growth were found, such as necking and competitive growth, and there is a high consistency of dendritic morphologies between simulation and experiment. Meanwhile, we analyzed the influence of parameters on dendritic morphology.

In order to simulate the gradual expansion of the crack in ductile material which should take the affect of elastic-plastic and geometric nonlinearity into account, the EWK damage model was used as the fracture criterion to instead of stress intensity factors or J integral theory in this paper. Let this criterion be a subroutine of ABAQUS’ main program and kept the two in real time communication in finite element algorithm. When some elements was met the fracture criterion in subroutine, let the Young’s modulus of these elements be “zero” in main program to simulate physical fracture. One kind of Newton method which was suit for localized unstable problems was used in this algorithm. Taking the tensile fracture of a rectangular sheet with a elliptical hole in its center as an example, A numerical result is obtained. The result shows that the effect of the fracture is according to the actual physical phenomena and the path of fracture is consistent with the prediction of analytical solution.

Materials modeling and simulation have been widely used in studies on microstructure evolutions of conventional polycrystalline materials, but very few reports for uses in nanocrystalline materials. Based on our previous analytical model that describes the thermodynamic functions of nanograin boundaries (X.Song, J.Zhang, L.Li, et al, Acta Mater. 2006, 54(20), 5541-5550), the thermodynamic features of nanograin boundaries were introduced into the Cellular Automaton algorithm. With the hybrid model, the quantitative and visual simulations of nanograin growth have been carried out in this article. The simulation results show that the nanograin growth kinetics is different from the normal grain growth behavior in conventional polycrystalline materials. The nanograin growth exponent, n, is not a constant as in the polycrystalline metals which equals 2, but changes with the growing process, which has a range of 1.706.59. The excess free energy of the nanograin boundaries is the driving force for nanograin growth, which is closely related with the grain size. The simulation studies prove that the thermodynamic features of nanograin boundaries strongly affect the energy state of the nanocrystalline materials hence the nanograin growth kinetics, as a result of the nanoscale effect. It is considered by the authors that the simulations of nanograin growth should take into account the thermodynamic features of nanocrystalline materials.

Process principle of reciprocating spray forming large thick-wall tubular was analyzed. The distribution of the mass flux of spray cone and behavior of the deposit track of single layer were studied, a model of deposit of single layer was established on the basis of these research. Aiming at the model and the helix characteristic of the deposit track, the influences of model parameters （Mmax 、a 、d） and mandrel movement parameters （w、v） on the deposit behavior ,and the influences of mandrel radius on deposit thickness of single layer were analyzed. Through the simulating of the deposit thickness overlapped by the deposit profiles of multiple circumrotating cycles,the movement parameters（w、v）of tubular spray forming were optimized.