Many data on hydrogen solubility in pure metals usually used in Gasar process, such as Al, Mg, Cu, Ni and Fe, have been compiled. All data were transformed into the same form as lg[H]=-A/T+B+0.5*lg(PH2) , and good results for calculating solubility have been gained by averaging the values of solubility constant A and B respectively.

The process and characteristics of high-temperature ferrite (δ) → austenite (γ) phase transformation during cooling of an AISI30 stainless steel have been observed in-situ by using a confocal laser scanning microscope. The results show γ phase appears prior at the δ grain boundaries. The cooling rate affects the growth morphology of γ phase which representatively includes polygon, block-like, round, dendritic, plat-form, network, and calabash-like. The independent γ dendrite becomes coarse, and may converge with others surrounding γ dendrites. The convergence degree for the γ dendrite at the δ grain boundary is clearly higher than that in the grain at the same cooling rate. The secondary dendrites become coarse, and grow competitively during cooling. The growth interface becomes unstable as the cooling rate increases. Meanwhile, the movement rate increases, along with the sudden rise and then fall of temperature.

Copper ball bonding is an alternative interconnection technology that serves as a viable and cost-saving alternative to gold wire bonding which is commonly applied in microelectronic packaging. In this paper, 50μm copper wire were bonded to the Al+1%Si+0.5%Cu pad successfully by thermosonic wire bonding. Scanning Electron Microscopy, Energy Dispersive X-ray Spectrometer and Micro X-Ray Diffractomer were adopted to investigate the intermetallic compounds (IMC) at the interface of wire and pad. The results show that Cu/Al IMC growth followed the parabolic law as a function of aging times at certain aging temperatures, Cu/Al IMC growth was more sensitive to the aging temperature than the aging time, the activation energy of Cu/Al IMC growth was 85Kcal/mol and the major forming IMC were CuAl2 and Cu9Al4.

The TiN/O′-Sialon electroconductive composite were fabricated by pressureless sintering from TiN/O′-Sialon powder that was synthesized by the carbothermal reduction nitridation method using high titania slag as the chief raw material. Phase assembly and microstructure were analyzed by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The effect of TiO2 content in initial raw materials on densification, mechanical properties and electrical conductivity were studied. The results show that O′-Sialon and TiN exist in the sintered samples. The O′-Sialon grains exhibit equiaxied morphology and the grain size is about 1~3mm. The TiN particles show fine granular morphology, with most of the grains lower than 0.5mm in size. For the composite samples sintered at 1500℃ using raw materials containing 30wt%TiO2, bulk density, hardness and flexure strength is 3.1g/cm3, 9.2GPa and 169MPa, respectively. The minimum amount of TiO2 in initial raw materials is 25wt% for the formation of electroconductive network in the composites. The electric resistivity of such a composite is 1.8×10-2Ω·cm.

Energetics and electronic structures of Ni/Ni3Al interface with additions of Re and Ru have been investigated by a first-principles plane-wave pseudopotential method. The calculated rupture works W show both of that either Re substitutes for Ni in g-Ni block or Ru replaces for Al atoms in g¢-Ni3Al block are profitable to improve the strength of the Ni/Ni3Al interface. In the case of the multiple alloying of Re and Ru, it is found only the mode of Re and Ru, respectively, occupying at Ni and Al sites at (001) atomic layers adjacent to the coherent (002) interfacial atomic layer can further enhance the Ni/Ni3Al interface. While Ru locates at Al sites in g¢-Ni3Al block and far away from the coherent (002) interfacial layer, it is found the multiple alloying of Re and Ru not only do not elevate the strengths of Ni/Ni3Al interface with addition of Re or Ru but make them decrease to a lower value than that of clear Ni/Ni3Al interface without addition as well. A deep analysis of electron densities of states (DOS) and the distributions of valence electron densities of Ni/Ni3Al interface before and after alloying reveals that the effect of Re and Ru alloying on the rupture strength of g-Ni/g¢-Ni3Al interface can be attributed to the change of the interlayer bonding in the interfacial region induced by strong electron interactions within first nearest neighbor (FNN) Re-Ni and Ru-Ni atoms, respectively, compared with FNN Ni-Ni and Ni-Al.

In the super-long fatigue life regime (106~109 cyc), the fatigue behavior of the as-extruded ZK60 Mg alloy was studied. The results revealed that a plateau existed in the regime of 5×106 ~ 108 cyc, whereas the fatigue strength gradually decreased in the regime of 108~109 cyc, and the fatigue strength corresponding to 109 cyc was 90±5MPa. SEM fracture observation indicated that the fatigue crack mostly initiated at the surface or subsurface for the samples failed in the regime of 5×106 ~108 cyc, and at the interior non-metallic inclusion for the samples failed between 108 and 109 cycles. According to the observation and determination of the region size of the crack initiation, the fatigue strength was estimated, and compared with the experimental result.

The effect of macrostructure and casting temperature on susceptibility to hydrogen flaking、the fracture toughness, KIQ, and threshold stress intensity factor of hydrogen induced delayed cracking, KIH, have been investigated. The result shows that casting temperature can influence the susceptibility to hydrogen flaking, which of the last billet is higher then that of the first billet. There is evident effect of macrostructure on the susceptibility to hydrogen flaking, which is the maximum in thezone of cylindrical grain and the minimum in the zone of equal-axis grain. There are no effect of the macrostructure and casting temperature on hydrogen diffusivity, Da, the fracture toughness, KIQ, and the threshold stress intensity factor of hydrogen-induced delayed cracking, KIH.

A series of TiN/Si3N4 nano-multilayers with different Si3N4 modulation thickness were reactively deposited by magnetic sputtering in order to study the sensibility of mechanical properties of TiN/Si3N4 multilayers on the change of Si3N4 thickness. The microstructure of the multilayers was characterized with X-ray diffraction, high-resolution transmission electron microscopy and scanning electron microscopy. A nanoindentor was introduced to measure the mechanical properties. Results show that when the thickness is less than 0.7 nm, Si3N4, normally amorphous in deposition state, could form a NaCl-type pseduocrystal structure due to the template effect of TiN crystal layer. Crystallized Si3N4 layers and TiN template layers grow coherently into columnar crystals with (111) preferred orientation. Correspondingly, the hardness of the films was enhanced to a maxim value of 38.5 GPa, showing a superhardness effect. Further increasing Si3N4 layers thickness, the coherent interfaces of the multilayers were damaged and Si3N4 layers become amorphous, accompanying by the decline in the hardness of the coatings.

Superhard nanocomposite Ti-Si-C-N coatings were deposited on substrate of high speed steel using an industrial pulsed d.c. plasma chemical vapor deposition set-up. Detailed microstructure examined by means of XRD, XPS and TEM suggested that the Ti-Si-C-N coatings are a nanocomposite structure composed of nanocrystalline Ti(C, N) and amorphous carbon and Si3N4, occasionally h-Si3N4. Ti(C, N) showed a strong 200 preferred orientation. With Ti content increasing and Si content decreasing, high-temperature oxidation resistance gain improvement gradually. When Ti and Si contents were 17.8at. % and 8.7at. %, respectively, nanocrystals of Si3N4 in the coating were dispersed on an amorphous matrix.The kind of coatings exhibited a much higher temperature (900℃) oxidation resistance. The possible origin of high-temperature of Ti-Si-C-N coating is explained that with increasing Si content, increasing amorphous Si3N4 thickness/layers and h-Si3N4dispersed in the matrix act as an efficient diffusion barrier against oxygen diffusion, which is helpful for improvement of oxidation resistance. Two-stage oxidation process involving mass gain and loss were observed, and the failure of the coating took place in the process of mass loss in the coating.

Analytical electron microscope (AEM) was applied to investigate the effect of excess free carbon on the microstructure of SiC fiber during SiC deposition growth and relation between microstructure and strength of SiC fiber. The results indicate excess free carbon addition can make effects on microstructure in two aspects. One is that carbon addition can effectively avoid WO3 formation at W/SiC interface, and then, as a result, get rid of oxygen element in fiber; the other is that it can reduce grain size of SiC, especially adjacent to W core. In addition, many concentric C rich layers form within inner SiC sheath. Above changes in microstructure play a positive role in improving fiber’s strength Key words: SiC fiber, analytical electron microscope (AEM), microstructure, strength.

Cold deformation can effectively enhance the strength of austenitic stainless steels. In this paper, a high nitrogen austenitic stainless steel with 1.0wt.% nitrogen and the 316L stainless steel were investigated on their microstructures, true stress-strain curves and micro-hardness after compressive deformation at room temperature. It was found that both the mechanical twins and the slips participated in the deformation for both two steels under the deformation less than 20%, but the slips turned to be dominant for 316L when the deformation was increased to 50%, the high nitrogen steel still remaining the above two mechanisms. There was no α’ martensite transformation in the high nitrogen steel under deformation, showing better structure stability, but there was martensite in the 316L. The strength, the micro-hardness and the work-hardening effect of the high nitrogen steel were much higher than those of the 316L, and the strength could be largely enhanced by cold deformation for the two steels. The micro-hardness was related to the crystal orientation for the two steels and the effect of crystal orientation was larger than that of the microstructure inhomogeneity. The mechanism of the high nitrogen stainless steel showing excellent properties was also analyzed and discussed.

Cu43Zr43Al7Pd7 bulk metallic glass (BMG) with a diameter up to 5mm was successfully prepared by copper mold casting. The glass-forming ability (GFA) and thermal stability of the BMG obtained were investigated by means of XRD, DSC and DTA. It is shown that Cu43Zr43Al7Pd7 system exhibited an excellent glass forming ability as indicated by high values of Trg (=0.607) and γ (=0.417) as well as supercooled liquid region(Tx= 75K), respectively. Uniaxial compressive test revealed that the BMG obtained possesses pretty good mechanical properties with a fracture strength of 1877 MPa and an overall strain of 4.9%, respectively. Electrochemical measurements were carried out in 1mol/LH2SO4 and 3%NaCl aqueous solutions by potentiadynamic polarization at room temperature. It is shown that Cu43Zr43Al7Pd7 BMG exhibited spontaneous passivation in both solutions with wide passive regions. The passive current densities are about 10-6～10-5 A/cm2, which are much lower than that of Cr18-Ni8 stainless steel, implying a good corrosion resistance.

Combining MAEAM with MD simulation method, both the relaxed structure and strain energy of an a[100] edge dislocation in BCC metal Mo have been simulated systematically in atomic scales. The results show that the relaxed structure has a C2V type group symmetry.Calculated strain energy Es per unit length of the dislocation is a linear function of ln(R/2b) while radial distance R≥1.5b=4.72Å, thus the corresponding core radius is determined to be rc=4.72Å. From intercept and slope of linear fitting those data corresponding to the outside of the dislocation core, we further infer the dislocation core energy Ecore=1.6334eV/Å, K=0.10eV/Å3, the latter is in agreement with the elasticity theory prediction (K=μ/4π(1-υ)=0.088eV/Å3).

The variations and distributions of viscosity in PIM filling process are given by numerical simulation of PIM filling process for intricate part. The relation between the final distribution of viscosity and the defects in PIM are analyzed. The results of the simulation showed that the pressure in the cavity heightens sharply at the near end of the filling stage, and then the distributions of velocity and viscosity change rapidly accordingly. As a result of these changes, the distribution of viscosity at the end of the filling stage is very complicated. There are some small areas which viscosity is higher than nearby areas’ in the melt flowing central region. And the process of forming the high viscosity areas and the changing of their geometrical shape are studied. It shows that the powder-binder separation or the density gradients in the component may occur during PIM process.

By multiphase field model, the stable and non-stable growth of eutectic CBr4-C2Cl6 alloy is simulated. The simulated results of stable growth are accordant with Jackson-Hunt’s eutectic theory，which proved that the model is reliable. As to the non-stable growth under varying growth velocity, the results show that, during step increase or step decrease in velocity, the mechanism of the lamellar spacing adjustment is through abrupt lamellar branching or progressive merging and annihilation accompanied the growing up by itself, respectively, moreover, there exists strong asymmetry between these two processes during lamellar adjustment. At the moment of step changing in velocity, the adjustment of lamellar spacing, the average velocity and the average interface undercooling characterize the hysteresis effect.

In order to investigate the metal flow behavior during extrusion process with active friction, numerical simulations and experiments were employed to investigate the mechanical mechanism of the extrusion process with active friction. The characteristic quantity such as the second invariant of the deviatoric stress tensor (J2)、Lode parameter( ) were employed for the division of deformation area. The results show that when extruding with active friction, no metal flow interface forms at the container bottom, the dead metal zone completely disappears, the deformation type of the metal in the plastic deformation area changes from three to the tension type, and the homogeneity of the deformation as well as metal flow is greatly improved. Therefore, it will be easy for extruding and promoting the extrudates quality.

Non-sinusoidal oscillation factor was introduced into non-sinusoidal oscillation to make it take on the virtues of optimum mode, so the determination of it is very important to actualizing high speed casting with high quality. Combined with actual data and a non-sinusoidal oscillation profile with virtues of optimum mode, oscillation process parameters and friction force in mold were analyzed, rational factors at 1.8 m•min-1 and 2.0 m•min-1 casting speed adopted this profile were given, and the rule of factor change when the casting speed increased was also discussed. The results show that the rational factor at 1.8 m•min-1 and 2.0 m•min-1 casting speed was 0.2, it is consistent with practical system, under the situation of frequency and amplitude invariable, the factor should be increased to 0.25 to ameliorate oscillation effect real time when casting speed enhanced to 2.2 m•min-1 from 2.0 m•min-1.

Solute diffusion controlled solidification model were applied to simulate the initial stage cellular to dendrite transition of Ti55Al45 alloys during directional solidification at different velocities. The simulation results show，during cellular/dendritic transition , mixed structure zone composed of cells and dendrites was observed ，with two parallel closely spaced dendrites with secondary dendrites absent at the facing surfaces . The dendrite spacing are larger than that of cellular spacing at a given rate, the columnar grain spacing sharply increases to a maximum as solidification advance to coexistence zone. In addition, simulation also revealed the numbers of the seeds also exert an influence on the grain spacing, with increasing the numbers of the seed, the uniform degree of the columnar grain spacing tends to increase. Lastly the main influence factors of affecting cellular/dendritic transition were analyzed, which could be dendrite growth resulting in slight fluctuations of liquid composition occurred at growth front. The simulation results also are in reasonable agreement with experiment observation at low cooling rates.

An improved model of calculating solid fraction is presented in this paper that the solid fraction of solid/liquid interface zone can be expressed as an second order equation of one variable based on calculating phase diagram, instead of calculating the solid fraction based on the assumptions of the position and the shape of the solid/liquid interface, which make the physical meanings of the model more clearly. Using the model the solidification microstructure and solute microsegregation of U-6%Nb binary alloy are simulated. The simulated results show that Nb concentration in the initial nucleated position is high. As the solidification proceeds, Nb concentration of the nucleus decreases continuously due to the back diffusion in the solid phase. At the end of solidification, there are poor Nb concentration zones formed at the grains boundary where Nb concentration can be lower than 3%.