Dislocation structures, effective and internal stresses of cyclic strained ferritic stainless steel

journal article - other

en

The hysteresis loops of ferritic X10CrAl24 were digitally recorded and analysed in order to separate the effective and internal. By means of the „Generalised statistical theory of the hysteresis loop” the average characteristics such as the effective elastic modulus Eeff, the saturated effective stress es and the probability density function f(ic) in relation to the number of cycles and ap, were determined. The cyclic plastic response of ferritic steel can be accurately described by this statistical theory (high es ≈ 255 MPa). As for the ferritic steel, the second local maximum of f(ic), was revealed. This phenomenon was discussed together with an observed dislocation arrangement by TEM methods, the orientation of crystals was determined by Kikuchi lines. The dislocation structures were studied in cyclical deformed polycrystalline ferritic stainless steel X10CrAl24 using transmission electron microscope (TEM). Specimens were strained in plastic strain amplitude ap controlled tests (symmetric tension-compression) at room temperature to failure. Thin foils were prepared from specimens cycled with plastic strain amplitudes = 1∙10–5, 2∙10–5, 1∙10–4, 5∙10–4, 1∙10–3, 3∙10–3, 1∙10–2. In dependence on ap three basic dislocation structures were identified. Nevertheless space dislocation arrangements at low ap change into bunch dislocation loops, veins, walls (labyrinths) and cell dislocation arrangements prevail at high.

The hysteresis loops of ferritic X10CrAl24 were digitally recorded and analysed in order to separate the effective and internal. By means of the „Generalised statistical theory of the hysteresis loop” the average characteristics such as the effective elastic modulus Eeff, the saturated effective stress es and the probability density function f(ic) in relation to the number of cycles and ap, were determined. The cyclic plastic response of ferritic steel can be accurately described by this statistical theory (high es ≈ 255 MPa). As for the ferritic steel, the second local maximum of f(ic), was revealed. This phenomenon was discussed together with an observed dislocation arrangement by TEM methods, the orientation of crystals was determined by Kikuchi lines. The dislocation structures were studied in cyclical deformed polycrystalline ferritic stainless steel X10CrAl24 using transmission electron microscope (TEM). Specimens were strained in plastic strain amplitude ap controlled tests (symmetric tension-compression) at room temperature to failure. Thin foils were prepared from specimens cycled with plastic strain amplitudes = 1∙10–5, 2∙10–5, 1∙10–4, 5∙10–4, 1∙10–3, 3∙10–3, 1∙10–2. In dependence on ap three basic dislocation structures were identified. Nevertheless space dislocation arrangements at low ap change into bunch dislocation loops, veins, walls (labyrinths) and cell dislocation arrangements prevail at high.

dislocation structures, probability density function, effective and internal stresses,CYCLIC STRAINED ferritic steel, hysteresis loops

2002

01.07.2001

1429-6055

72

279/2001

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