According to characteristic crystal theory of alloy phases established on the statistic thermodynamics and electronic theory of metals,a systematic analysis has been conducted on the Au-Cu system. The interaction equations of characteristic properties (energy and volume),electronic structures and their changing characters of characteristic atoms in the Au-Cu alloys have been determined. The theoretical values of heat of formation, mixing Gibbs free energy and lattice constant as a function of concentration are in good agreement with the experimental values.XIE Youqing, professor, Department of Materials Science and Engineering, Central South University of Technology, Changsha 410083

On the basis of the model of atomic cluster jump theory,a microdynamical model of crystal growth rate was developed under condition of the dynamic solidification.The classical continuous growth model seems to be only one of the special case.Theoretical analysis showed that the crystal growth rate is dependent on not only the nature of metal but also the supercooling,△T, and external force, F. Certain solidification behaviours of columnar crystals and columnar dendrites under fluid flow condition are explained by using of the model.JIAO Yuning, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015

The microstructure of RS Ti_3Al-base alloys prepared by the hammer-and-anvil technique has been studied. The as-RS microstructures of the alloys are quite different to the as-cast one. First, the grains of the RS alloys are finer. Secondly, the Ti_3Al-base alloys with D0_(19) structure in normal condition have transformed fully into ordering orthogonal martensite α″in the RS microstructure. And then, α″,α″+β0, or β0 has been observed sequentially in the RS Ti_3Al-Nb alloys according to the addition of Nb,the strong β-isomorphous stabilizer of Ti,and the APBs in β0 in the RS Ti_3Al-Nb alloy are finer.CUI Yuyou, Institute of Metal research, Chinese Academy of Sciences,Shenyang,110015

The morphology of γ' precipitate changed from cubic to flower like dendritic shape during high temperature ageing for a Rene'N4 single crystal Ni-base superalloy.The dendritic growth of γ' precipetate was of the selection area characteristic. The analysis results indicated that there was a critical growth size a* of γ' precipitate.As soon as the size of γ'was larger than the value of a * , the γ' precipitate would hollow and split by dismatch dislocation in order to match the increase of systematic energe of γ' and develop into dendrite.YU Xihong. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015