Fe-Cr-Ni合金の歪誘起<I>FCC</I>(γ)→<I>BCC</I>(α′)変態と活動すべり系

Abstract

Relations between the strain-induced γ→α′ transformation and active slip systems have been studied by optical and transmission electron microscopy on Fe-18%Cr-14%Ni single crystals and 18-8 type stainless steel polycrystals. The results obtained are summarized as follows: (1) The minimum strain to induce the γ→α′ transformation is larger in a crystal oriented for single slip than in the one for double slip. (2) α′-plates in a crystal oriented for single slip are wide and long needle-like, and those in the one for double or cross slip are small and lenticular. All of them are formed in banded structures on the well-developed slip bands. (3) Many slip bands are emitted on the primary slip bands from interfaces between a newly-formed α′-plate and γ-matrix. In this case, the slip band emitted from a larger α′-plate is longer and wider. (4) Stacking faults that randomly occur on primary slip planes from interfaces of both sides or one side of an α′-plate are frequently observed. (5) Many dislocations run parallel with the primary slip plane of γ-matrix inside and in the surrounding area of an α′-plate. Furthermore, in the latter area, overlapping stacking faults and ε′-plates are similarly formed. (6) Thin α′-plates are generally formed in the regions where secondary slip bands terminate on primary slip bands. Even though secondary slip bands in this case belong to two different kinds of systems, most of α′-plates formed in the regions are of the same variant. (7) A nucleation side edge of an α′-plate is straight on the well-developed slip bands.On the basis of the above phenomena, stress relief by α′-phase formation is mainly discussed.