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

100%

Petrenec M. , Polák J.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

2001

tom z. 72

129-133

The hysteresis loops of ferritic X10CrA124 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 [sigma es] and the probability density function f(sic) in relation to the number of cycles and [epsilon ap] were determined. The cyclic plastic response of ferritic steel can be accurately described by this statistical theory (high [sigma es] = 255 MPa). As for the ferritic steel, the secon local maximum of f([sigma 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 X10CrA124 using transmission electron microscope (TEM). Specimens were strained in plastic strain amplitude [epsilon ap] controlled tests (symmetric tension-compression) at room temperature to failure. Thin foils were prepared from specimens cycled with plastic strain amplitudes = 1x10-5, 2x10-5, 1x10-4, 5x10-4, 1x10-3, 3x10-3, 1x10-2. In dependence on [epsilon ap] three basic dislocation structures were identified. Nevertheless space dislocation arrangements at low [epsilon ap] change into bunch dislocation loops, veins, walls (labyrinths) and cell dislocation arrangements prevail at high.

Vliv podmínek zatěžování na strukturu lité niklové superslitiny

80%

Petrenec M. , Podrábský T. , Hrbáček K.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

2002

tom z. 75

85-88

Cyclic strain localization in cast nickel based superalloy INCONEL 792-5A at room temperature

80%

Petrenec M. , Man J. , Obrtlík K. , Polák J.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

2005

tom z. 86

269-274

Cylindrical specimens of cast polycrystalline superalloy INCONEL 792-5A were cyclically strained under total strain control at room temperature up to fracture. Cyclic hardening curves were documented. Dislocation structure was studied with the technique of oriented foils in TEM. SEM was used to investigate surface relief topography. The cyclic stress-strain response is characterized by initial hardening followed by the stabilized stress response. Surface persistent slip markings and slip bands lying along {111} planes in the interior of grains cut both channels and precipitates. Experimental results concerning the surface relief and dislocation structure are used to discuss the stress-strain response.

In-situ testing and heterogeneity of UFG Cu at elevated temperatures

70%

Petrenec M. , Král P. , Dvořák J. , Svoboda M. , Sklenička V.

Journal of Achievements in Materials and Manufacturing Engineering

2014

tom Vol. 62, nr 2

69--74

Purpose: The motivation of present investigation is the study of deformation-induced processes during in-situ tensile and compression test at elevated temperature in order to elucidate the role of the microstructure changes during creep testing. Design/methodology/approach: Experiments were conducted to investigate deformation-induced processes during in-situ tensile test at elevated temperature. Findings: It was found that creep resistance of UFG pure Al and Cu is considerably improved after one ECAP pass in comparison with coarse grained material, however, further repetitive pressing leads to a noticeable deterioration in creep properties of ECAP material. Researches limitations/implications: In the present work was found that ultrafine-grained microstructure is instable and significant grain growth has already occurred during heating to the testing temperature. Originality/value: The experiments conducted on pure Al and Cu found that their creep resistance is considerably improved after one ECAP pass in comparison with unpressed material.