MECHANISM OF THE INTERPHASE-BOUNDARY SLID ING IN 2-PHASE (GAMMA ALPHA) STAINLESS-STEEL BICRYSTALS/

The aim of the present study is to obtain a fundamental knowledge abou t sliding characteristics along the austenite (gamma)/ferrite (alpha)- interphase boundary which may play a variety of roles in high temperat ures and superplastic deformations of a two-phase(gamma/alpha) stainle ss steel. Sliding of the interphase boundary has been studied by a sim ple shear test under constant loads at 1373 K, employing bicrystals wi th the (gamma/alpha)-interphase boundary produced by a solid-solid dif fusion method. The experimental results could be analyzed through the power law of upsilon proportional to tau(n), where V is the sliding ve locity and tau is the shear stress. The value of n was estimated to be approximately 2. Local plastic deformation in the alpha-phase and no plastic deformation in the gamma-phase neighboring to the interphase w ere observed. Metallograpy after the sliding test showed that no recry stallization occurred in the alpha-phase neighboring to the interphase -boundary. Appreciable void formation was observed along the slid inte rface. Furthermore, the activation energy of the sliding was estimated to be close to that of the bulk self-diffusion in alpha-phase. These facts suggest that the behavior of interphase-boundary sliding is clos ely associated with ductile deformation of a thin layer of the alpha-p hase in the immediate vicinity to the interface, rate-controlled by cl imb motions of dislocations arrested along the interphase-boundary.