The local deformation bands formed ahead of crack tip both in ferrite and in austenite were in situ observed under TEM during deformation process of a ferrite-austenite duplex stainless steel. It is dominated by crack tip Schmid factors, dislocation shielding latent hardening and hardening coefficient. If the crack tip slip system was preferably activated by pure mode Ⅱ resolute and the decreasing rate of hardening coefficient was enough, then the local deformation band ahead of crack tip was easy to be formed.

The microstructure of a rapidly solidified single crystal Ni-base superalloy treated by laserglazing has been observed by TEM and STEM-EDAX techniques.Various morphologies of extraordinary flower-like MC carbide (TiC) were revealed in the narrow interdendritic regiom. While the superfine γ' precipitate and higher density.of dislocation were found in the γmatrix.

Effect of rare earth on the middle-temperature internal friction of commercially pure iron is closely related to heat treatment. The rare earth additive was resulted for acting on alloying. The Snoek-Ke-Koster (briefly called SKK) peak is found to remain still even if the deformed iron after furnace cooling has undergone to age at 600℃ for 1h. The SKK peak temperature does not simply fall as the ascending of aging temperature, but raise up again at 600℃ aging.

The influence of longitudinal and torsional bias stresses on anomalous amplitude-dependent internal friction was studied. The longitudinal bias stress may always weaken the anomalous amplitude-dependent effect, while the torsional one may induce different effects from different directions applied. Bias stress effect exhibits only in such alloy undergone proper heat treatment or cold working. The anomalous amplitude-dependent internal friction peaks, P_3, P_2 and P_1, are found to be related closely to slant dislocation kink chains. Thus, the application of bias stress to internal friction would be contributed to studying dislocation structure.

The precipitation and dissolution together with their control of the primary η-phase in the high-Ti Ni-Fe-Cr based superalloy have been investigated. The precipitation of primary η-phase is found to be related closely to Ti or Al content and solidificaion rate of the alloy. Collection of block η-phase may remarkably reduce the tensile strength, ductility and rupture life of the alloy. The temperature-time relation of dissolution of the primary η-phase obeys T=1370-86.1 lg t for as-cast superalloy.The formation of primary η-phase may be prevented by reasonable control of Ti or Al content and smelting process. The adoption of treatment under hot deformation and homogenization may be the remedy for unfavourable influence of η-phase.

Study was made on the swerving of strength and hardness vs parameter P=T(20+lg t) curves of L-M for long-time aged 20Cr11MoVNbNB steel at 550, 600,650℃, where T being aging temperature in K and t being aging time in h. It seems obviously due to: (1) coarsening of mean size of principal precipitate M_(23)C_(6), (2) precipitation of Laves phase MoFe_2, (3) decrease of solution Mo content in matrix and (4) recovery and recrystallization occurred.

An additive of Y to Ni_3Al based alloy may form a phase YNi_5 which increases in amount with the increase of Y content. It was found that the YNi_5 phase in Ni_5Al alloy could remarkably make its grains finer and its grain boundaries more crooked other than straigh. If the Y content≤0.1 wt-％, it occurs as solid solution state and is favourable to high temperature compressive properties and oxidation resistance of the alloy. While Y≥0.3 wt-％, the formation of YNi_5 is predominant in the shape of irregular strips inside Ni_3Al grains and along their grain boundaries. This seems to be quite harmful to high temperature strength, ductility and oxidation resistance of the alloy.

Based on the experimenial data, it was clarified that the plastic strain ratio R-value is not equal to Hill's γ-value for Ti sheet. From the non-quadratic orthotropic yield function proposed recently by the author, an optimal expression between yield stress and γ-value for Ti sheet was developed on overall investigation. The suituble value of exponeat in the function seems to be 6-8. Thus, an equation was suggested to estimate strength for the pressure vessel to be made of Ti sheet.

The wear of Cu-based CuZnAl shape memory alloys under dry sliding against steel was found to be plasticity-dominated, with adhesion and delamination being the two main mechanisms. Adhesion was observed to be accompanied by metal transfer. TEM observation on tensile test of thin foil showed that the stress-induced martensitic transformation occurred from β-phase in the vicinity of pre-existing microcracks. The blunt effect of crack tips may be proposed to explain the wear of CuZnAl shape memory alloy due to preferential orientation reaction of variants in martensite and stress-induced martensitic transformation in β-phase.

The eutectic growth of cast iron during rapid solidification has been studied with laser remelting and deep etching. A new mode of the mushroom eutectic growth was revealed other than the usual honeycomb and lammellar ones. The mushroom eutectic growth may finally form the lamellar dendrite structure.

The fractal structures formed in rapidly quenched Al_(86)Mn_(14) alloy have been observed by SEM. Their fractal dimensions are from 1.46 to 1.97. The principal phase is icosahedral quasicrystalline one, examined by TEM and X-ray diffractometer,in addition to a small amount of Al phase. It is believed that these fractal structures are formed by many aggregate particles during the rapid-quenching process.

The microstructure, strength-toughness and fatigue properties of an ultrahigh strength steel 40CrMnSiMoVA have been investigated. The so-called eta-bainite,composed of thin rareined austenite films within or between the bainitic ferrite laths was found in the steel after isothermally quenched at 300℃ for 1h. In comparison with the martensite structure obtained by isothermally quenching in martensite range,the meta-bainite has more excellent strength and plasticity, lower notch sensitivity, stronger strain hardenability, higher fatigue strength, longer strain or impact fatigue 1ife, slower crack propagation rate and more remarkable overload effect on increasing fatigue life.

Fatigue crack propagation rate, d~α/d~N, and threshold stress intensity range, ΔK_(th), of 20CrMnMo steel coniaining low carbon martensite or low carbon martensite/bainite (LCM/B) duplex structure, obtained by O. Q. and austempered at 360℃,have been meaured using specimens under four-point bending. Observation was also made of the crack path and fracture morphology with relation to microstructure. The formation of LCM/B duplex structure, which caused by 20％ lower bainite after shorttime isothermal treatment, may remarkably increase ΔK_(th) and considerably decrease d~α/d~N. The effect of microstructure on d~α/d~N and ΔK_(th) was discussed with the mphasison the crack propagaion path.

The mechanical reduction of CuO by pure metallic Mg has been investigated during pulverizing in ball mill at room temperature. The reduction was towards its completion of an average particle size down to 20nm after 32h. The mechanism of mechanical reduction of oxide seems to be proposed as the surface activation of nm sized particles driven by mechanical force.

Crystallization behaviour of rapidly solidified Fe C-Si-Mo alloy ribbon, made byasingle roller method, together with its changes in phase and hardness has been studied by Xray difftaction and SEM. Results show that the alloy attributes its very high Vickers hardness to numerous fine carbides formed during crystallization.

The influence of mechanical activation on the leaching behaviour of scheelite was studied by means of fine grinding in an attritor and subsequently HCl leaching in the presence of PO_4~(3-). Results showed that after fine grinding in the attritor, the reaction rate of scheelite with HCl-Na_3PO_4 was remarkably increased, the extraction of W was increased from about 8 to 99％. The IR spectra and X-ray difftaction analysis indicated that in addition to an enlargement of surface area the fine grinding action had made also changes of fine structure and reactivity of solid surface, hence the leaching process of scheelite can be carried out under mild leaching conditions.

Interaction of Cu_2S with Cu_2O was investigated in the range of 1150 to 1250℃. The reaction rate increases with the increasing of surface area of Cu_2O grains and depends unobviously on the temperature. At the suggestion of the controlling step of reaction rate being oxygen diffusion through the liquid layer along interaction boundary, two final kinetical equations would be made as follows: α=6.69×10~(-2) At for 0 References | Related Articles | Metrics

An attempt was made on applying the Wilson equation to predict the thermodynamic properties of ternary liquid alloys. The activity of each component in ternary liquid alloys was found to be conveniently calculated from the equation with the related binary bimolecular interaction parameters. The calculated values are in fair agreement with experimental data, and are verified to be reliable by the criterion of classical thermodynamics.

Thermal analysis has been adopted to determine the liquidus and eutectic temperature of Fe-20％ Cr-Mn alloy over range of Mn and C contents. Using regression analysis, the partial quasi-binary phase diagrams of Fe-Mn alloy (solidification range) have been constructed. And the effect of Mn content on liquidus and eutectic temperature was discussed.

An investigation was carried out of the resistance to cyclic oxidation of the as-cast normal-grained Co-30Cr-5Al alloy substrate at 1000℃ in air together with its sputtered coating of microcrystallized CoCrAl alloy grains sized less than 0.5μm.Acoustic emission counts showed that the initially formed Al_2O_3 scale on the bare alloy substrate cracked and spalled severely off after only one or two cycles on cooling, and then the worse protective layer of Cr_2O_3 and CoCr_2O_4 spinel occurred on surface. While such substrate coated with sputtered microcrystallized CoCrAl alloy film was not damaged under oxidation even through 100 cycles at 1000℃. In comparison with the normal-grained alloy, the microcrystallized alloy coating of similar constitution exhibite more excellent resistance to oxide spalling on surface.

The effects of the stress components on the nucleation sites and propagation directions of stress corrosion cracks in brass were investigated with specimens under mode Ⅱ and mode Ⅲ loadings. Results indicated that: under mode Ⅱ loading, stress corrosion cracks nucleated on the site with maximum normal stress component and propagated along the plane perpendicular to the maximum normal stress; under mode Ⅲ loading, the stress corrosion crack was not evident on the 45°plane due to the general corrosion in aqueous solution with high NH_4OH concentration, while stress corroded in aqueous solution with low NH_4OH concentration, numerous cracks with spacings of 10-150μm were found on the 45°plane with maximum normal stress and no stress corrosion cracks was observed on the plane with maximum shear stress.

Comparative investigations were ca1ricd cut of tLe efItct of Leat 1reatment regimes for GC--4 steel, 40CrMnSiMoVA, on its c1ack p1opagating ratcs, from corrosion fatigue, (da/dN)..' or stress cor1osion crackirg, (do/dt),.,', in mcdia with various constituents and VH va1ues. Both (da/dN).. 8'r d (do/dt),.. acce!cra1e wi1h tbe increase of yieId stress of the steel, yet the fOraner js far 1ess tLan 1Le l8tcr. ]n ccmparison with mcdia, tLe (do/dt),,. in distil1td water is sligLt1y grca1cr 1Lan tbat in 3.5% NaCl solution, and tLe (dQ/dN)., in distil1cd water is far less ttan tkat in 3.5% NaCl solution. With the pH value increasing in 3.5% NLCl ao1ution, 1le (do/dN). F lQwerS down and the (da/dt),.. specds up. An xplahation was a1Eo r1oroltd witb concept of the cyclic bardening and softeniDg at crack tip, as we1l as the crack c1osure and occluded ceU effect.

Effect of carbon content in substrate, made of 7 steels separately, on thel chemica vapour deposition of TiN has been investigated. The increment of deposition rate is linearly related to the increase of carbon conient in own substrate. The α-Fe peak, besides TiN, is revealed in X-ray diffraction pattern of the TiN coating.The (220) preferred growth of TiN deposited on Cr12MoV steel substrate increases with the increase of depositing temperature. Only Ti energy spectrum is found from the bright region at coating surface and the interior, while both Ti and Fe energy spectra from dark region.

A much higher elongation of warm-rolled superplastic Al-Li-Cu-Mg-Zr alloy was made under two-stage strain rate tests comparing with the single ones.During initial stage of deformation, a deformation-induced continuous recrystallization which converted a subgrain structure into a recrystallized grain structure by a conitnuous increase in boundary misorientations had occurred. The higher the strain rate is, the faster the continuous recrystallization and the finer the recrystallized grains will be. The fine recrystallized grain structure formed duringthe first stage deformation is the essential condition for the material to have high strain rate hardening and strain hardening during the low second hardening superplastic deformation. The combination of strain rate hardening and strain hardening is the reason why the higher elongation may be obtained during two-stage superplastic deformation of the alloy.

The buffer layer material itself may be influential to the bond strength between active brazing filler and ceramics. For Ag_(57)Cu_(38)Ti_5 filler metal, Cu or Ta is excellent buffer layer material, but Kovar or Ni-15Cr-15Co is worse. It was important to design a layer of soft buffer, such as Cu, to relax interfacial stress rather than hard buffer layer, such as Mo, to avoid stress. There is an optimum thickness range of soft buffer layer, saying h/L=0.02-0.1. It was a good solution to the interfacial stress problem to use soft/bard buffer layer to increase metal/ceramics joint strength. Finally, an idea of designing gradual materials as buffer layer between metal and ceramics was suggested.

On the basis of fluid kinetics, a model for infiltration kinetics of liquid metal into fibre prefabricated composite has been proposed. The infiltration processing, together with the measurements of infiltrating velocity and permeability, for the C fibre-reinforced Al matrix composites have been studied. The model proposed seems to be in good agreement with the experimeatal results. Two different infiltration modes, uniform and non-uniform, were found and a new technique was suggested.Thus, the quality composites of C fibre-reinforced Al may be made under low pressure regardless of non-wettability of liquid metal to the fibres.

The recovery recrystallization of 3 deformed Ni-Cr-Co superalloys with different Co contents has been studied using positron annihilation technique and TEM.The alloys with low Co content have more defects occurred than ones with high Cocontent, and the former may be faster in dislocation recovery than the later. Thus,the apparent activation energy of recrystallization increases with the increase of their Co content in alloys. The relationship botween apparent activation energy and stacking fault energy together with their effect on recovery were also discussed.

The phase diagrams of binary systems SmCl_3-CaCl_2 and SmCl_3-LiCl was determined by DTA and X-ray diffraction analysis. The system SmCl_3-CaCl_2 is of a simple eutectic type with eutectic point of 55.8 mol-％ SmCl_3 at 545℃. The system SmCl_3-LiCl is of the type with incongruent melting phase 2SmCl_3·LiCl at peritectic point 434℃ and with eutectic point of 31.5 mol-％ SmCl_3 at 395℃.

Isotherm section at 25℃ of phase diagram and phase structure of the Bi-Pb-Tlternary system have been studied by means of room and high temperature X-ray diffractionand quenching.

One of the chief characteristic peaks of high-caustic-ratio and highly oncentratedsolution in Raman spectra is that of 470 cm~(-1). By comparison with the Raman spectra of crystalline solid Ca_3[Al(OH)_6]_2 and Ba_2[Al_2(OH)_(10)], it can be concluded that Al(OH)_6~(3-) ion and perhaps also the polymers of Al(OH)_6~(3-) ions may be formed in high-caustic-ratio and highly concentrated sodium aluminate solution.

The ultrafine alloy powders, CuRh, γ-Ni_(0.33)Fe_(0.66) and α-Fe_(0.66)Co_(0.33) of size less than 35 nm were prepared by reduction of complex metallic oxides under atmosphere of 15％H_2 and 85％ Ar.