Korol Y. Conditions for short-range ordering of stacking faults in cobalt alloyed by substitution elements

A set of the scientific papers are championed presenting the results of study of the effect of the cooling rate, high-temperature -phase state, and alloying on short-range ordering (SRO) of stacking faults (SF) in the low-temperature -phase of Co-based alloys with substitution elements. On the basis of the study of the samples differing in chemical composition, two groups of the elements were found, which are characterized by their effect on the ordered arrangement of SF. The SRO features were demonstrated to be independent of the conditions and stage of polymorphous transition in the case Co was alloyed by elements Sn, Ta and Nb of which the diffusive mobility is low in cobalt. It was shown theoretically that the ordered arrangement of SF in -phase of such alloys could be stimulated by the SF interaction through electron subsystem. The SF ordering that has not been observed in Co-based alloys previously was revealed in the alloys containing elements having high diffusive mobility (Co-Ge, Co-Si). The threshold interrelations between the SRO characteristics and the cooling rate were found. A model of SF ordering in а-phase of Co-based alloys was developed with allowance made for a redistribution of the alloying atoms during transition. The redistribution was shown only to govern the SF ordering in a range of the cooling rates.