The slip systems of Nb single crystals with single and multiple glide orientations have been investigated respectively under tension, compression and cyclic defomation. From the stereographic plots of the slip line directions measured around the specimen surface,the slip planes were determined. The slip system for the single glide orientation ([321] orientation) is(101) under tension, however in compression, it is(101) and (213) . The relationship of the slip systems activated by tensile,compressional and cyclic deforination was analyzed in accordance with the deformation features of bcc crystals. The surface topography of the specimens has been observed using optical microscope, SEM and TEM(replical).The activated sequence of the slip systems for the multiple slide orientation ([110] orientation) was therefore determined. Correspondent: WU Jiansheng, professor, Department of Malerials Science, Shanghai Jiao Tong University, Shanghai 200030

Two different negative interactions in alloys GH30 and GH34 were observed under prior creep followed by fatigue and under continuous cyclic creep,respectively.The exponent of the fatigue damage, for the former, in the interaction term is much large than that of the creep damage, and hence the negative interaction is mainly as a result of the sequential fatigue damage being restrained by the prior creep. While the exponent of the creep damage,for the latter, in the interaction term is much large than that of the fatigue damage, and hence as a result of creep damage being partly recovered by the fatigue (cyclic loading and unloading). The microscopic origin of the two different negative interactions has been explained in the light of microscopic observations. Correspondent: KONG Qingping, professor, Institute of Solid State Physics, Chinese Academy of Scicnces,Hefei 230031

Fractal analysis is adoped to study the change of dendrite grain boundary configurations at different solidification rates in two kinds of superalloys. It is found that fractal dimensions of the grain boundaries in both of the alloys increase with the increase of solidification rates. In addition, the relationship between the fractal dimensions of the grain boundaries and the system entropy in the solidified superalloys is discussed from the physical defination of fractal dimension. Correspondent: SUN Liling, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015

According to the bond energy formula of the empirical electron theory of solids and molecules, the mechanism of order-disorder transformations is analysed from the results of the bond energy and the bond structures of the alloys. The Fe-Al binary alloys have an order-disorder transformation which is resulted in the change of numbers of covalent electron pair on bonds. Correspondent: ZHANG Jianmin, Department of Materials Scicnce, Institute of Materiurs Science, Jilin University, Changchun 130023

The internal friction at 400-850℃ in high-pure Fe-Nb-C alloys has been measured, and a large stress-dependent magnetomechanical hysteresis damping peak of which the peak temperature varies from 666 to 740℃ as strain amplitude changes was discovered. The conditions of the peak appearing and disappearing, some characters of the peak and the effect of some factors such as ascending and descending temperature, frequency,amplitude, defoimation and annealing etc. on the peak have also been studied. The method to determine the internal stress σst and σi obstructing Barkhausen jumps of domains by internal friction experiment and the physical mechanism producing the magnetomechanical hysteresis damping-temperaturepeak in the alloy were proposed. Correspondent: JI Jingwen,Department of Physics, Northeastern University, Shenyang 110006

Through analysing the present dynamic models concerning isotherinal martensitic transformation in ferrous alloys, the instantaneous value of embryos formed by autocatalytic effect has been proposed on the basis of affiiming the mechanism of the autocatalytic nucleation. The new model makes the dynamic equation more simple in form and clear in meaning. The numerical calculation combined with the experimental data has indicated that the theoretical curve is well in agreement with experimental results. Correspondent: WANG Liuding, associate professor, Department of Applied Physics, Morthwestern Polytechnical University, Xi'an 710072

The tensile properties of two-phase (γ＋γ＇) Ni_3Al(B)-Cr base alloys containing Zr, Mg and RE have been studied. Experiments show that Ni_3Al(B)-Cr-Mg-RE alloy as compared with Ni_3Al(B)-Cr-Zr alloy, the yield strength does not decrease, the mopohology is changed from bulky irregular γ＇- phases to fine spherical γ＇- phases and the percentage of elongation is increased about 20%. Correspondent: CHEN Junming, professor, Shanghai institute of Metallurgy, Chinese Academy of Sciences, Shanghai 200050

An infrared thermographic system was used to monitor the process of fatigue compressing of high strength steel pressure vessel under working pressure. The IRCE effect obtained by themography at the beginning of fatigue testing can detemine the stress concentrated areas. The leaks in the vessel under compressing may testify that the examination of the stress coneentrated area by thermography is available. The fatigue softening and hardening effect was found in the tests.The thennographic results for the stress distribution of cylindrical thin-wall pressure vessel is in agreement with that computed by the Glogal coordinate system. It is believed that the fatigue exercise effect under working pressure may prolong the working life of the pressure vessel. Correspondent: HUANG Yi,associate professor, Institute of Metal Research, Chinese Academy of Scicnces, Shenyang 110015

The effect of anodic and cathodic polarizations on the ambient creep of brass in 3.5% NaCl and CH_3COOH＋CH_3COONa solutions has been investigated. The results showed that the creep rate in both solutions increased linearly with the increase of the anodic current density and was approximately inversely proportional to the square of radius of the specimen. The dε/dt in 3.5%　NaCl solution was much higher than that in CH_3COOH＋CH_3COONa solution at the same anodic current density. The creep rate resulting from dislocation climb induced by vacancy supersaturation during the anodic polarization has been calculated as follows:dε/ dt = Aβi / r2whereA=8παMρDs△t(2△r)(1/2)／c0dFZln(L／), and β is a constant related to the degree of dezincification. The experimental data support the proposed mechanism. Cathodic polarization could also increase the ambient creep of brass by a mechanism related to hydrogen-facilitated local plastic deformation. Corresponaent; GU Buao,Department of Materials Physics, University of Science and Technology Beijing,Beijing 100083