화학공학소재연구정보센터
Materials Science Forum, Vol.426-4, 2741-2746, 2003
High strength and good plasticity of L1(o), ordered alloys provided by preliminary strong cold deformation
Specific features of the microstructure and the deformation behavior of the L1(0) type alloys (NiPt, FePd, CoPt, CuAu) ordered after a strong cold deformation were studied. When the disordered alloys were subjected to heavy (60-95%) drawing, the ultimate strength and plasticity of ordered alloys were 1500-2200 MPa and 25-40% respectively. Significantly, the dislocations, which were inherited from the disordered alloy, proved to be incomplete in the superlattice. As a result, they lost mobility and formed a rigid framework. A possible mechanism, by which mobility of dislocations influences recrystallization, was proposed. TEM examination allowed determining an optimal structure of the ordered alloys: fibers, cells in the fibers, and lamellae in the cells. It was found that the lamellar structure (more precisely, a set of parallel boundaries of twin-like c-domains) plays a considerable role of a damper. It is the absence of the lamellar structure in L1(2)-type alloys that makes it impossible to use this method for improving their properties. This method was compared with other known methods used to enhance the strength and plasticity. To a certain extent, the proposed method resembles the so-called trip-effect (transformation-induced plasticity). However, a diffusionless martensitic transformation, which occurs during deformation and causes formation of a two-phase structure, is used in trip steels. The structure under study resembles most textile constructional composites reinforced with a space framework. Conditions, which may provide an optimal state in other superstructures, were formulated.