With undercooling increasing, the undercooled Ni-50%Cu alloy underwent two grain refinement processes. One occurred in the undercooling range of 50 -100 K and the other one at the undercoolings higher than the critical value 220K where the refined crystal possesses the dendritic substructures. It is suggested that the tendency to remelting of the primarily formed dendrite can be evaluated with the dimensionless superheating of the earliest frozen part in the dendrite stems during recalescence. The dimensionless superheating increases first and then decreases with increasing undercooling, and its highest value corresponds to the undercooling range in which the first grain refinement takes place. Both the thermodynamic analysis and the crystal cotheuration indicate that the grain refinement at low undercoolings is caused by the remelting of solid and that at higher undercoolings by stress which leads to the disintegration and recrystallization of the primary dendrite.

The amorphous NiTi thin films were fabricated by dc/ac magnetron sputtering.Mechanical properties of 51.6%Ni-Ti thin films annealed at 550 ℃ for 0.5 h were studied. Bend deformation and stress/strain experimental results indicated that the free-standing NiTi thin films have good shape memory effect, and the recovery rate of shape memory was nearly 100%. The shape memory properties of the film and bulk NiTi alloy are approximately at the same level.

The dislocation configuration in a single crystal Ni base alloy with (100) plane parallel to stress axis during primary creep has been investigated by TEM. The results show that the 1/2<110> dislocations are activated on the octahedral slip systems in the 7 matrix channels and multiplied by the dislocation reaction. The dislocations motion must overcome greater resistance and dislocations move in a form of cross-slip and shorter distance, because the normal γ matrix channels of (100) planes are subjected to compression stress. After dislocation loop in tensile stress matrix channels moves into compression stress matrix channels by means of cross-slip, both sides of the dislocation are pinned and it is simillar to the F-R dislocation configuration.

This paper presents a study of dislocation behavior in a plastic zone ahead of a crack-tip in a Co-base superalloy during in situ deformation in a TEM. The results show that the dislocations emitted from the crack-tip are partials when the tensile acs is [51]. However,when the tensile axis is [121], the dislocations from the crack-tip are perfect, which will extend during their motion toward the matrix. The stress state ahead of the crack-tip and its effect on the dislocation behavior in the plastic zone were also analysed.

A special deflection device for TEM has designed and used to study the dislocation configuration change before and after recharging hydrogen. The relations among hydrogenfated microcrack initiation, dislocation motion and dislocation free zone (DFZ) were also studied. The results showed that hydrogen can promote dislocation emission and motion. When the dislocation emission and motion develop to a critical condition, hydrogen-facilitated microcrack will initiate in DFZ or at the top of the ored. This process is similar to that during tensile testing in the air.

The effect of boron doping on the sensitivity to environmental embrittlement of Co3Ti alloys was investigated. The results show that the boron doping in Co3Ti does not have the effect on suppressing environmental embrittlement. The hydrogen diffusion coefficients in Co3Ti alloys with and without boron measured by a new experimental method have almost the same value, which indicates that boron in Co3Ti alloys does not reduce the hydrogen diffusivity along the grain boundaries. The susceptibility of boron-doped Co3Ti alloys to moisture-induced environmental embrittlement is attributed to no boron atoms segregating to the grain boundaries.

The fatigue crack propagation rate has been measured for A537 steel in 3.5%NaCl solution at an applied cathodic potential of -1400mV(SCE) under different cyclic overload occurrence ratio(OCR). The fracture surface characteristics have been analyzed by SEM. When OCR=10-l and 10-2, the crack growth was accelerated and some brittle characteristics such as cleavage and intergranular cracking were observed on the fracture surface. However, for OCR=10-3,2×10-4 and 10-4, the crack growth was retarded, and the pearlite morphology appeared on the fracture. The difference of cracking models between ferrite and pearlite in A537 steel could be the enrichment of hydrogen atoms at the interphase of ferrite and cementite.

Sodium attack of both aluminium (99.999%, 99.8% and 99.5% purity) and Al12%Si alloy is investigated. Aluminium of 99.999% purity is immune, but alumililum of 99.8%or 99.5% purity and the Al-Si alloy are attacked by molten sodium at 350 - 500℃. The corrosion product formed on the surface of the materials is identified as the AlNaSi compound.This suggests that sodium attack of both aluminium and Al-12%Si alloy is the result of a reaction between sodium and the silicon contained in the aluminium.

The two-phase Cu-50Cr alloy in air at 70─900℃ was corroded nearly parabolically, except at 900℃ when the instataneous parabolic rate constat decreased with time. The scales were consisted of an outer layer of copper oxide and an inner layer of a copper oxide or double oxide Cu2Cr2O4, in which the particles of chromiumare surrounded by chromia and the double Oxide Cu2Cr2O4. A nearly continuous Cr2O3 layer only appears at interface between the scale and matrix at 900℃. The formation of a continuous outer layer of chromia was more difficult on two-phase M-Cr alloy than single-phase M-Cr alloy.

The device of zone melting directional solidification has been used to investigate the preferred orientation, microstructure and magnetostriction of Tb0.3Dy0.7(Fe, M)1.95 (M=Al,Mn, B) metallic compound. When the temperature gradient GL≈700 K/cm, the growth velocity V mm/min, the crystal grows in plannar interface, 1< V 6 mm/min, in cellular morphology; V=8 - 12 mm/min, in primary dendrite; V > 15 mm/min, in developed delldrite. As V=12 mm/min, GL≈1000 and 400 K/cm, the crystal grows in cellular morphology developed dendrite, respectively. Crystals in cellular morphology are <110> preferred orientation and poor magnetostrictive property. Crystals in primary dendrite with <112> preferred orientation, have a good performance, the maximum value of magnetostriction (A) is 0.00175. Crystals in developed dendrite with part <112> orientation have an inferior property than the former.

Phase equilibrium relationships and compositions of α2(α)/γ inl the Ti-Al-Cr ternary system between 1000 -1300℃ have been determined by using diffusion couple and EPMA method. The panal isothermal sections of the Ti-Al-Cr system and the partial vertical diagram of the Ti-Al system with Cr content smaller than 10% in the temperature range have beed drawn. The results confirmed the rule of the distribution ratio of Cr in α2(α) andγ phases and supported the vieWpoint that Cr occupies Al site and thus reduces Al content in γ-TiAl.

Using the atomic radii, principle quantum number of valance shells, the number of d-electrons and f-electrons as the inputs of artificial neural network and trained by known data of liquidus and solidus curves, the liquidus or solidus curves of the binary alloy systems of transition metals with continuous solid solutions can be predicted correctly.

The constitutive behavior of semisolid slumes depends on a number of macroscopic factors. These factors translate to internal variables and external variables that govern the rheological behavior of the material. Internal variables include a measure of the degree of agglomeration among solid pericles, fluid phase viscosity, particle size, particle morphology, and distribution of particle sizes. External variables are temperature and shear rate. According to the different characters of semisolid slurries, we can give the corresponding new models under the different conditions on the basis of the primary models.

The effects of nonstoichiometric ratio x on the structure, thermodynamic properties for the alloys MmBx (Mm=mischmetal, B=Ni0.72Mn0.08Co0.14Al0.06, x=4.2 - 5.5) and the charge-discharge performances of metal hydride electrodes were investigated. With x value decreasing, the unite cell volumes and the enthalpy (-ΔAH) of hydride formation increased. The relationship of plateau pressure and x of the alloys can be expressed as Inpeq= 1. 99 2x - 11. 131. Asx<5.0, the second phase Ce2Ni7 with high electrocatalytic activity segregated in small numbers in the alloys. The electrodes of nonstoichiometric alloys (x<5.0) had more capacity and superior activation than those of MmB5 and MmB5.5. At x=4.8, the nonstoichiometric alloy electrode had the maximum capacity of 274.7 mA.h/g.

Isothermal sintering method was used to study the initial stage sintering of a soft and a hard agglomerated α-Al2O3 powder with a diameter of 10 nm. For both powders the initial stage sintering was found to be controlled by grain boundary diffusion. Activation energies of grain boundary diffusion of the soft and the hard agglomerated powders were determined to be 354 and 481 kJ/mol respectively and the diffusion coefficient of the soft agglomerated α-Al2O3powder from 900 to 1200 ℃ was estimated.

Constant heating rate sintering and conventional sintering methods were used to investigate the sintering kinetics of α-Al2O3 powder with a mean particle diameter of 10 nm.Constat heating rate (10℃ /min) sintering shows that densilication of the greenbody mainly occurs between 1200 and 1450℃. Relative density of the specimen is 98.85% after conventional sintering at 1400 ℃ for 2 h. Theoretical analysis indicates that further increase of the greenbody density and improvement of microstructural homogeneity could lead to a substatial decrease of sintering temperature of the powder.

The correlation between initial permeability μi and temperature T (μi-T curve) for nanocrystalline Fe72. 7 Cu 1 Nb2 V 1. 8 Si13. 5 B9 alloy annealed at 5 30 ─ 6 20℃ was investigated.The experimental results showed that the annealing temperature Ta has significant effects on μi-T curve. Three types of μi-T curves were observed. The corresponding annealing temperatures are (1) Ta=530 - 550℃t, (2) Ta=560 - 590℃ and (3) Ta 2600℃. The phase structure of alloy corresponding to the three types of μi-T curves was analysed and the effects of the grain size and volume fraction of α-Fe(Si,V) phase as well as the magnetic properties of residual amorphous phase on μi-T curve were also discussed.

By carbothermal method, the NbCx(x=0.95) whiskers were prepared in graphite resistance furnace under 0.1 MPa/N2 ambient atmosphere at the temperature range of 1120 1670℃. The diameters and lengthes were 50 -1700 urn and 5 -312.5μm respectively. The effect of preparation processing on the apparent morphology and growing machanism of whisker was presented.

The improvement of short-fibre reinforced composite materials under weak interface was discussed. Comparison between plain short-fibre model and dumbbell short-fibre model has been done. Effectivity of dumbbell model under different strength ratios of mains to fibre was discussed. born abate element analysis it was concluded that dumbbell model could well improve the performance of composite materials with weak interface. The lower strength ratio of mains to fibre, the better -improvement is.

Variations of hyperfine-field with tempering temperature for high strength high fracture toughness steel G99 were studied by Mossbauer spectroscopy. The precipitation of alloy carbides was observed and analyzed by TEM and EDS. The results show that the distribution ofhyperfine-field and the quality of carbides and austenite within steel G99 vary with increasing tempering temperature. These are mainly caused by the increase of Fe atoms neighboring with Co or Ni, the decrease of Fe atoms neighboring with Cr or Mo, the solution of cementite, the precipitation of alloy carbides and the arising of reverted austenite. The important factors that the steel G99 has superior combinstion of strength and toughness are the precipitation of fine alloy carbides M2C, the arising in small amouats of reverted austenite, and well-distributed Co and Ni atoms in tempered martensite.

The positron lifetime spectra of several Al-Fe-V-Si-Mm alloys with different content of Misch metal was measured, and the effect of the amount of Misch metal on the positron lifetime in Al-Fe-V-Si-Mm alloys was discussed.