A study in a certain range of temperature and strain rate was made of thePortevin-Le Chatelier effect in the sheet specimens as-quenched or further pur-posely aged for a short-term of a commercial Al alloyc ontaining 4.19% Cu and1.25% Mg.It resulted that the ripple marking formation on the surface of thesheet may be delayed by the further short-term aging after quenching.Thus,thedynamic strain aging process is likely to delay the happening of inhomogeneousdeformation band on the alloy sheet.

The influence of Mn content on the transition temperature,martensite mor-phology and substructure as well as the shape memory effect in Cu-Al-Zn-Mn-Nialloys has been investigated by means of electrical resistance measurement,opticmicroscope and TEM observations.Experimental results showed that with theincrease of Mn content,the transition temperature decreases considerably and thetemperature range of the thermoelastic martensite transformation broadens;themartensitie morphology is being perfected from the parallel plates into the self-accommodation configuration;and the martensitic substructure undergoes atransition from twin to stacking fault Wpe.The perfection of the self-accommo-dation,the size of martensitic variant as well as the quenched-in vacancies havea remarkably influence on the shape memory effect of the alloys.

The properties of gas carbonitriding layer on 18CrMnNiMoA steel relatingto its morphology,structure,composition,distribution and partition of alloyingelements among the phases contained have been studied by means of electrolyticextraction-chemical separation-X-ray diffraction phase analysis layer by layer,aswell as by TEM or electron diffraction observation and by chemical analysis.Thestrengthening mechanism of the carbonitriding layer has also been discussed.

The effect of plating factors on the structure of electrodeposited.Ni-Mo orNi-W alloy has been studied.It was found that the pH value is a decisive oneamong factors whether the deposited alloy can be made or not as amorphous struc-ture.The changes in the structure still seem to be explained by the model pre-viously developed by the authors to interpret the structure of the Ni-P depositedlayer.

The constitution and its effect on properties of elastic Nb-base alloy Nb-40Ti-5.5Al were examined by means of metallography,electron microscopy,X-ray dif-fraction analysis of chemically extracted phases and electron diffraction of thinfoil.The results showed that the heat treating temperature dependence of consti-tution of the alloy indicated as follows:annealing at≤400℃ for 1 h after cold-rolled with 70% reduction,no marked change is revealed;heat treating between550—700℃ for 1 h,an age-hardening peak is noted;annealing at 1000℃ for 1h,the fully recrystallized solid solution is detected;further isothermal annealingat 650—750℃,the age-hardening and the precipitation of strengthening phase as(Nb,Ti)_3Al in the grains are obtained;and during isothermal aging at 650℃,thegrain boundary precipitation is characterized obviously.The internal stress in thealloy facilitates the phase precipitation.The post age-hardening tempering maycause the return phenomenon.

ZHANG Yansheng Institute of Metal Research,Academia Sinica,Shenyang

The penetration depth λ(T),coherent length ξ(T),high critical field H_(c2)(T)andcoefficients k_1(T)and k_2(T)of the type II superconductors at low temperature werecalculated by the generalized G-L equations.An expression of the structure of avortex line at low temperature was derived.The lower critical field H_(c1)(T)was eval-uated by some simplified assumptions.The effect of the impurities on λ,ξ,k_1,k_2and H_(c1)was also discussed.After the calculation,it shows that the Werthamer'sand Wang's equations are no longer valid while the applied field H_0 approachesto H_(c2)(T)at low temperature.

A quantitative study of the carbide particle cracking was performed on fourdifferent spheroidized carbon steels deformed uniaxially in tension.The local crit-ical stresses for the carbon particle cracking were estimated.Based on these obser-vations and computations,the effect of microstructure on the carbide particlecracking was also discussed.

The hydrogenated polycrystalline α-Ti was in situ observed under SEM toobtain a better understanding of its tensile fracture microprocess,principally,ofthe correlation of contents between overall H_2 and hydride,of the effect of hy-dride on the crack nucleation and propagation,as well as of the behaviour ofthe deformation and fracture microprocess caused by hydride.It was found that:(1)The crack nucleation in the polycrystalline α-Ti with H_2 content less than152 ppm is irrelevant in the hydride.It is ductile cracking and conforms to theslip mechanism.While its H_2 content more than 727 ppm,it is brittle cracking,controlled by the hydride and belongs to the nonslip mechanism;(2)In α-Ti withlower H_2 content,the transgranular crack propagation along a zigzag pathforward is controlled by maximum shear stress.On the contrary,in α-Ti withhigher H_2 content,the crack is intergranularly propagated still along a zigzagpath forward,yet lost its ductile feature.

The kinetics of conversion of galena into lead carbonate in(NH_4)_2CO_3 solu-tions was studied using electrochemical method with a rotating ring-disc electrode.Reaction mechanism was proposed based on the results of transient polarizationstudies.A mathematical model was derived to simulate the steady state polariza-tion curves obtained.The oxidation of sulphide to sulphate should be proceeded in a number ofsteps with the formation of intermediate products,A rotating ring-disc electrodewas used to detect the intermediate products with galena as the disc electrode andAg as the ring electrode.Experimental transient polarization curves with a scan-ning rate of 10 mV/s have shown that at 0.49,0.86 and 1.19V(SHE)curfentpeaks were observed on the disc electrode and ring electrode respectively.Basedon the previous work and the experimental results obtained,it has been assumedlthat the first current peak of polarization represents the oxidation of leadsulphide to elementary S with PbCO_3 and S formed on the electrode surface aspassivation film.It is considered that the 2nd current peak of polarization curves representsthe conversion of S to PbSO_4 with lead carbonate and sulphate as the possiblepassivation film.The 3rd current peak has not been studied thoroughly in thepresent work.On steady polarization curves only one current peak(at 0.28V)was found.A kinetic equation for the anodic reaction based upon the mathema-tical model proposed has been derived as follow:(?)The reaction is 2nd order with respect to the NH_4~+ concentration and 1storder with respect to OH~- concentration respectively.When the electric potentialsapplied are rather low,the last two terms of the denominator may be neglected.Calculation based on this simplified equation has been found to represent theexprimental results satisfactorily.

The properties of the spin glass systems in equilibrium state were studied bymeans of Monte-Carlo simulation and Metropolis sampling.The temperature depen-dence of the susceptibility and specific heat was computed for the spin glass sys-tems where the host of hcp lattice is non-magnetic,the number of lattice pointsN=9×9×9×2,and the concentration of magnetic impurity x=0.5,1,2,3,5,8,10 and 15 at.-%.Using Heisenberg model,it was assumed that NX magneticatoms are located at the lattice points randomly and homogeneously.It was alsoassumed that the only interaction between spins is the RKKY long-range oscillatoryexchange with an interaction length R_0=3a.The deviated method was used incalculation for a group of temperature each time in order to Save time.The calcu-lated curves of susceptibility and specific heat are consistent with the correspond-ing experiments fairly well.

Measurements of the electrical resistivity,its temperature dependence and the tran-sition temperatures at different stages of some amorphous alloys,such as Zr_(100-x)M_x(M=Fe,Co,Ni,Cu or Pd),Cu_(100-x)Ti_x,Pd_(83.5-x)Si_(16.5)M_x(M=Cu,Ag,Ni,Pt,Rh,Ru,Ir,Os,Hf,Ta,W or Re)and Pd_(80-x)Si_(20)Cr_x prepared by the meltspinningtechnique were made in the temperature range of 0—500℃.The effects of minoradditives on them are also discussed.

Kinetics of the magnetic permeability decay of an amorphous alloy Fe_(76)Si_(10)B_(14)at temperature range of 50-300℃ was examined.The evidence of isochronalstructural relaxation spectra as the origin of the magnetic permeability decay wasobtained.The most probable activation energy and the distribution of activationenergy were calculated.By using the two-level-one-configuration model developedby Kronmüller,the reversibility of this type of relaxations was discussed.Theorigin of the decay was also analyzed.

Experimental results for atomic magnetic moment,Curie temperature,T_C,andcoefficient B of the T~(3/2)term in the Bloch law for amorphous alloys Fe-M-B(M=Cr,Mo or W)prepared by the drum spinning technique are reported.Theaverage magnetic moment for each metal atom is 2.0,-3.96,-4.62 or -4.08μ_B for Fe,Cr,Mo or W respectively in the three amorphous alloy systems.Thedecrease of T_C is at the rate of 20.5K/at.-% Cr,27.7K/at.-% Mo,or 26K/at.-%W with increasing Cr,Mo or W content respectively.These results are discussedin the light of a‘mixed’model due to C.W.Chen.The effect of the magneticshort range order around T_C is clearly observed by applying an external magneticfield.The coefficient B increases with the concentration of Cr,Mo or W,whichis interpreted as a consequence of weakening of exchange coupling between themagnetic atoms.

The stress relief and ductile-brittle transformation of the metallic glasses Pd_(82.5)M_1Si_(16.5)prepared by spinning roll have been examined.It was found that theductile-brittle transformation temperature,T_B,and activation energy,△E_B,of theglasses composed by the preceding transition metals,e.g.,Hf,Ta,W,Re,are in-creased markedly and by the later ones,e.g.,Os,Pt,influenced slightly,but byIr,T_B is decreased too many.The mode of ductile-brittle transformation of themetallic glasses PdSi_(16.5)is different among themselves composed by the precedingand later transition metals.The comparison of the influences of additives on theirtemperatures and activation energies of the ductile-brittle transformation and glasstransition has been made.These behaviours have been discussed on the basis ofthe Gaskell′s model and the Engel-Brewer′s electron theory of transition metals.

The electrical properties and crystallization of Cu_(0.60)Ti_(0.40)metallic glass wereinvestigated by X-ray diffraction,DSC technique and electrical resistance measure-ment under isothermal and isochronal heating conditions.A negative temperaturecoefficient of electrical resistivity of the metallic glass Cu_(0.60)Ti_(0.40)is presented,andit becomes positive and increasing value in process of crystallization.Its crystal-lization is shown in two stages and in conformity with he J-M-A equationbasically.A good mutual couforment about the activation energies of crystalliza-tion was made with calculation by various methods.It seems that there is agreat potentiality in the increase of the stability of Cu-Ti metallic glass.

A new method,namely,the step potential etching current mehtod for theindividual determination of σ-or M_(23)C_6-phase which is a difficult problem to sepa-rate each other by conventional chemical manner has been developed.This simpli-fied and rapid method easy to give certain information about the composition,con-tent and morphology of precipitated phases in the steel has been applied to stain-less steel samples.In addition,a formula for quantitative analysis was derived onthe basis of a new model of electrode process.The formula has been confirmedby experiments.

A computer program based on the matrix method is presented for analysingthe electron diffraction patterns with high order haue zone and the patterns fromtwo phases or twins.It is also used for analysis of the rotation in crystals.