Evolution of microstructure and residual stress during annealing of austenitic and ferritic steels

International audienceIn this work the recovery and recrystallization processes occurring in ferritic and austenitic steels were studied. To determine the evolution of residual stresses during material annealing the nonlinear sin 2 ψ diffraction method was used and an important relaxation of the macrostresses as well as the microstresses was found in the cold rolled samples subjected to heat treatment. Such relaxation occurs at the beginning of recovery, when any changes of microstructure cannot be detected using other experimental techniques. Stress evolution in the annealed steel samples was correlated with the progress of recovery process, which significantly depends on the value of stacking fault energy

Multireflection grazing-incidence X-ray diffraction: A new approach to experimental data analysis

The multireflection grazing-incidence X-ray diffraction method is used to test surface stresses at depths of several micrometres in the case of metal samples. This work presents new ways of analysing experimental data obtained by this method for Ni samples exhibiting significant elastic anisotropy of crystals. Three different methods of determining biaxial stresses and lattice parameter were compared. In the first approach, the calculations were performed using the linear least-squares method, and then two simplified procedures based on simple linear regression (weighted and non-weighted) were applied. It was found that all the tested methods give similar results, i.e. almost equal values of the determined stresses and lattice parameters and the uncertainties of their determination. The advantage of analyses based on simple linear regression is their simplicity and straightforward interpretation, enabling easy verification of the influence of the crystallographic texture and the presence of shear stresses, as well as graphical determination of the stress-free lattice parameter

A multireflection and multiwavelength residual stress determination method using energy dispersive diffraction

The main focus of the presented work was the investigation of structure and residual stress gradients in the near-surface region of materials studied by X-ray diffraction. The multireflection method was used to measure depth-dependent stress variation in near-surface layers of a Ti sample (grade 2) subjected to different mechanical treatments. First, the multireflection grazing incidence diffraction method was applied on a classical diffractometer with Cu Kα radiation. The applicability of the method was then extended by using a white synchrotron beam during an energy dispersive (ED) diffraction experiment. An advantage of this method was the possibility of using not only more than one reflection but also different wavelengths of radiation. This approach was successfully applied to analysis of data obtained in the ED experiment. There was good agreement between the measurements performed using synchrotron radiation and those with Cu Kα radiation on the classical diffractometer. A great advantage of high-energy synchrotron radiation was the possibility to measure stresses as well as the a0 parameter and c0/α0 ratio for much larger depths in comparison with laboratory X-rays. © 2018 International Union of Crystallography

Naprężenia własne w materiałach polikrystalicznych oraz ich zmienność podczas obróbki termicznej praca doktorska /

Tyt. z ekranu tytułowego.Praca doktorska. Akademia Górniczo-Hutnicza im. Stanisława Staszica (Kraków), 2012.Zawiera bibliogr.Dostępna także w wersji drukowanej.Tryb dostępu: Internet.Defekty struktury krystalicznej, ich powstawanie, ewolucja podczas wygrzewania, defekty struktury krystalicznej, punktowe, liniowe, błędy ułożenia płaszczyzn, powstawanie defektów, ich ewolucja w procesach aktywowanych termicznie, plastyczne formowanie metali, procesy termiczne porządkowania mikrostruktury, mechanizmy odkształcenia materiałów, odkształcenie sprężyste, plastyczne, modele odkształcenia sprężysto-plastycznego dla materiałów polikrystalicznych, odkształcenie ziarna polikrystalicznego, modele transformacji skali, oparte na relacji Hilla, sprężystoplastyczny model samouzgodniony, Lipiński, Berveiller 1989, algorytmy numeryczne, różnice między zastosowanymi modelami, założenia przyjęte w obliczeniach, pomiary tekstur krystalograficznych, idea pomiaru tekstury, pionierskie pomiary tekstury z użyciem dyfrakcji neutronów, naprężenia własne w materiałach polikrystalicznych, klasyfikacja naprężeń, dyfrakcyjne pomiary odkształceń sieci krystalicznej, ich związek z naprężeniami, geometria pomiaru, dyfrakcyjne stałe sprężyste, DSS, wyznaczanie naprężeń na podstawie zmierzonych odkształceń sieci krystalicznej, pomiary naprężeń dla próbek quasi-izotropowych, anizotropowych, zmodyfikowana metoda sin2ψ stosowana do pomiaru naprężeń w próbkach, jej rozwinięcie, wyznaczanie funkcji rozkładu naprężeń w metalach poddanych odkształceniom plastycznym, badanie naprężeń, tekstur w próbkach stalowych, pomiary tekstur, odkształceń sieci krystalicznej, analiza otrzymanych wyników bez uwzględnienia naprężeń niedopasowania plastycznego, wybór modelu krystalograficznego, dyfrakcyjnych stałych sprężystych, końcowe wyniki analizy, badanie naprężeń, tekstur w próbkach walcowanego mosiądzu, miedzi, pomiary dyfrakcyjne, analiza danych doświadczalnych, podsumowanie dotyczące procesu odkształcenia plastycznego, zmiany naprężeń własnych podczas wygrzewania próbek, procesy zachodzące w wygrzewanych próbkach stalowych, stal ferrytyczna, austenityczna, procesy zachodzące w wygrzewanych próbkach miedzianych, mosiężnych, miedź, mosiądz, podsumowanie dotyczące procesów zachodzących pod wpływem wygrzewani

Residual stress field in steel samples during plastic deformation and recovery processes

International audienceX-ray diffraction method was applied to measure residual stresses and stored elastic energy in deformed and annealed polycrystalline ferritic and austenitic steel samples. Orientation distribution of incompatibility stresses created during elastoplastic deformation was determined and presented in Euler space. Using deformation models, the second order stresses were correlated with different types of intergranular interactions occurring in the studied materials. An important decrease of the first and the second order residual stresses was observed during recovery and recrystallization processes. Diffraction peaks related to dislocations density were studied and correlated with stress variation during annealing process. Differences in stress relaxation between ferritic and austenitic samples were explained by different values of the stacking fault energy, which influences climb of dislocations

Intramuscular triacylglycerol in energy metabolism during exercise in humans

Multireflection grazing-incidence X-ray diffraction (MGIXD) was used to determine the stress- and strain-free lattice parameter in the surface layer of mechanically treated (polished and ground) tungsten and austenitic steel. It was shown that reliable diffraction stress analysis is possible only when an appropriate grain interaction model is applied to an anisotropic sample. Therefore, verification of the X-ray stress factors (XSFs) was accomplished by measuring relative lattice strains during an in situ tensile test. The results obtained using the MGIXD and standard methods ( and geometries) show that the Reuss and free-surface grain interaction models agree with the experimental data. Moreover, a new interpretation of the MGIXD results was proposed and applied for the first time to measure the probability of stacking faults as a function of penetration depth for a polished and ground austenitic sample. The XSF models verified in the tensile test were used in the analysis of residual stress components

Multireflection grazing-incidence X-ray diffraction: A new approach to experimental data analysis

International audienceThe multireflection grazing-incidence X-ray diffraction method is used to test surface stresses at depths of several micrometres in the case of metal samples. This work presents new ways of analysing experimental data obtained by this method for Ni samples exhibiting significant elastic anisotropy of crystals. Three different methods of determining biaxial stresses and lattice parameter were compared. In the first approach, the calculations were performed using the linear least-squares method, and then two simplified procedures based on simple linear regression (weighted and non-weighted) were applied. It was found that all the tested methods give similar results, i.e. almost equal values of the determined stresses and lattice parameters and the uncertainties of their determination. The advantage of analyses based on simple linear regression is their simplicity and straightforward interpretation, enabling easy verification of the influence of the crystallographic texture and the presence of shear stresses, as well as graphical determination of the stress-free lattice parameter