EBSD анализ микроструктуры аустенитной стали после прокатки в криогенных условиях

This work is based on the use of electron backscatter diffraction (EBSD) methods to investigate the microstructure of metastable austeniticsteel 12X18H10T (321) after cryogenic rolling. Cryogenic deformation was accompanied by martensitic transformations, and the martensitic phase nucleation mainly in deformation bands. It is assumed that the proceeding of the martensitic transformation in the most deformed parts of the microstructure should prevent the evolution of deformation-induced boundaries in the austenite and, thus, inhibit the process of fragmentation of this phase. Mechanical twinning was the primary (or even sole) mechanism providing HAB formation in the austenite

Effect of electric-current pulses on grain-structure evolution in cryogenically rolled copper

The effect of electric-current pulses on the evolution of microstructure and texture in cryogenically rolled copper was determined. The pulsed material was found to be completely recrystallized, and the recrystallization mechanism was deduced to be similar to that operating during conventional static annealing. The microstructural changes were explained simply in terms of Joule heating. A significant portion of the recrystallization process was concluded to have occurred after pulsing; i.e., during cooling to ambient temperature. The grain structure and microhardness were shown to vary noticeably in the heat-affected zone (HAZ); these observations mirrored variations of temper colors. Accordingly, the revealed microstructure heterogeneity was attributed to the inhomogeneous temperature distribution developed during pulsing. In the central part of the HAZ, the mean grain size increased with current density and this effect was associated with the temperature rise per se. This grain size was slightly smaller than that in statically recrystallized specimens

Анализ спектра разориентировок на основе удельной поверхности границ

The described method for analysis of misorientation distribution in terms of a specific grain-boundary surface has been used. It was found that this approach was effective for study of grain structure evolution during deformation, recrystallization and grain growth

Разделение механических двойников и двойников отжига посредством EBSD

The paper considers separation of mechanical and annealing twins through measuring the misorientation deviation at their boundaries from sigma3 by the electron backscatter diffraction (EBSD) method. The method is shown to be efficient in studies of partially recrystallized structures containing both twin types

EBSD investigation of microstructure evolution during cryogenic rolling of type 321 metastable austenitic steel

Electron backscatter diffraction (EBSD) was employed to establish microstructure evolution in type 321 metastable austenitic stainless steel during rolling at a near-liquid-nitrogen temperature. A particular emphasis was given to evaluation of microstructure-strength relationship.As expected, cryogenic rolling promoted strain-induced martensite transformation. The transformation was dominated by the γ→α′ sequence but clear evidence of the γ→ε→α′ transformation path was also found. The martensitic reactions were found to occur almost exclusively within deformation bands, i.e., the most-highly strained areas in the austenite. This prevented a progressive development of deformation-induced boundaries and thus suppressed the normal grain-subdivision process in this phase. On the other hand, the preferential nucleation of martensite within the deformation bands implied a close relationship between the transformation process and slip activity in parent austenite grains. Indeed, the martensite reactions were found to occur preferentially in austenite grains with crystallographic orientations close to Goss {110} and Brass {110}. Moreover, the martensitic transformations were governed by preferential variant selection which was most noticeable in ε-martensite. The sensitivity of the martensitic reactions to the crystallographic orientation of the austenite grains resulted in re-activation of the transformation process after development of a deformation-induced texture in the austenitic phase at high strains. Both martensitic phases were concluded to experience plastic strain which resulted in measurable changes in misorientation distributions. Cryogenic rolling imparted dramatic strengthening resulting in a more-than-sixfold increase in yield strength. The main source of hardening was the martensitic transformation with lesser contributions from dislocations and subboundary strengthening of the austenite