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1

Stochastic model describing evolution of microstructural parameters during hot rolling of steel plates and strips

Szeliga Danuta, Czyżewska Natalia, Klimczak Konrad, Kusiak Jan, Kuziak Roman, Morkisz Paweł, Oprocha Piotr, Pietrzyk Maciej, Poloczek Łukasz, Przybyłowicz Paweł

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e139

EN

Enhancing strength-ductility synergy of materials has been for decades an objective of research on structural metallic materials. It has been shown by many researchers that significant improvement of this synergy can be obtained by tailoring heterogeneous multiphase microstructures. Since large gradients of properties in these microstructures cause a decrease of the local fracture resistance, the objective of research is to obtain smoother gradients of properties by control of the manufacturing process. Advanced material models are needed to design such microstructures with smooth gradients. These models should supply information about distributions of various microstructural features, instead of their average values. Models based on stochastic internal variables meet this requirement. Our objective was to account for the random character of the recrystallization and to transfer this randomness into equations describing the evolution of dislocations and grain size during hot deformation and during interpass times. The idea of this stochastic model is described in the paper. Experiments composed of uniaxial compression tests were performed to supply data for the identification and verification of the model in the hot deformation and static recrystallization parts. Histograms of the grain size were measured after hot deformation and at different times after the end of deformation. Identification and validation of the model were performed. The validated model, which predicts evolution of heterogeneous multiphase microstructure, is the main output of our work. The model was implemented in the finite element program for hot rolling of plates and sheets and simulations of these processes were performed. The model’s capability to compare and evaluate various rolling strategies are demonstrated in the paper.

2

Usable Properties of AlSi7Mg Alloy after Sodium or Strontium Modification

Tupaj M., Orłowicz A. W., Mróz M., Trytek M., Markowska O.

Archives of Foundry Engineering

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2016

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Vol. 16, iss. 3

129--132

EN

The paper deals with the effect of microstructure diversified by means of variable cooling rate on service properties of AlSi7Mg cast alloy refined traditionally with Dursalit EG 281, grain refining with titanium-boron and modified with sodium and a variant of the same alloy barbotage-refined with argon and simultaneously grain refining with titanium-boron and modified with strontium. For both alloy variants, the castings were subject to T6 thermal treatment (solution heat treatment and artificial aging). It turned out that AlSi7Mg alloy after simultaneous barbotage refining with argon and grain refining with titanium-boron and modified with strontium was characterised with lower values of representative microstructure parameters (SDAS – secondary dendrite arm spacing, λE, lmax) and lower value of the porosity ratio compared to the alloy refined traditionally with Dursalit EG 281 and grain refining with titanium-boron and modified with sodium. The higher values of mechanical properties and fatigue strength parameters were obtained for the alloy simultaneously barbotage-refined with argon and grain refining with titanium-boron and modified with strontium.

3

On the influence of geometric microstructural properties of porous materials on the modelling of a tubular fuel cell

Karcz M., Kowalczyk S., Badur J.

Chemical and Process Engineering

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2010

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Vol. 31, z. 3

489-503

EN

A numerical model of tubular solid oxide fuel cell (SOFC) with simplified one-dimensional current flux prediction is examined. The model takes into account geometric properties of porous sinters used for anode and cathode. Three characteristic parameters, i.e. porosity, tortuosity and mean pore radii have been considered. The obtained numerical results allow one to estimate the influence of various geometric properties of porous materials on the fuel cell performance by means of average and local variables.

PL

Przedstawiono wyniki analizy numerycznej modelu rurkowego ogniwa paliwowego uwzględniającego podstawowe mikrostrukturalne parametry geometryczne porowatych elektrod. Rozważano trzy podstawowe parametry geometryczne: porowatość, krętość oraz średni wymiar porów. Uzyskane rezultaty umożliwiają ocenę wpływu poszczególnych wielkości charakteryzujących obszar porowaty na globalne osiągi ogniwa i lokalne wartości temperatury i gęstości prądu.

4

Statistical testing of microstructure differences

Klebanov L., Lechnerova R., Slamova M., Slama P., Benes V.

Inżynieria Materiałowa

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2008

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Vol. 29, nr 4

181-184

EN

In materials microstructures including particles the aim is to provide a statistical test whether two microstructures are different or not. The information included can be related to individual particle parameters as well as to their spatial distribution and intensity. Since in classical statistical testing the assumption of independence of observations is necessary which is not fulfilled here, we develop a new test based on TV-distances in probability theory. Using the measurement from a few of windows we consider a multidimensional two-sample test where each parameter of each particle corresponds to one dimension. According to the theoretical background of M-distances this situation can be converted to a univariate two-sample test. We present an application which consists in a comparison of metallographic samples of aluminium alloys.

PL

Celem pracy jest opracowanie testu statystycznego pozwalającego stwierdzić, czy dwie mitostruktury materiałów zawierających cząstki są różne czy nie. Test oparty na 7V-odległościach w teorii prawdopodobieństwa został opracowany na podstawie informacji na temat cech charakterystycznych cząstek z kilku ramek pomiarowych. Jego zastosowanie pokazano na mikrostrukturze cienkiej folii wykonanej ze stopu Al-Mn (rys. 1 i 2). Dokładny skład chemiczny badanego materiału podano w tabeli 1. Histogramy podstawowych charakterystyk (powierzchni przekrojów cząstek) przedstawiono na rysunku 3. Średnia powierzchnia i liczba obserwowanych przekrojów znajdują się w tabeli 2. Następnie został przeprowadzony nowy test o hipotezie zerowej zakładającej, że dwa zbiory danych obserwowane w ramkach pomiarowych należą do tej samej iriikrostruktury (rys. 4). Tabela 3 obejmuje wartości p dla tego testu, gdy rozpatrywane są trzy parametry jednocześnie oraz indywidualnie: powierzchnia, średnica równoważna i wskaźnik kształtu. Można wnioskować, czy hipoteza zerowa jest odrzucana, czy nie, i interpretować wyniki dla różnych materiałów.

5

Overconsolidation and microstructures in Neogene clays from the Warsaw area

Kaczyński R.

Geological Quarterly

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2003

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Vol. 47, No 1

43-54

EN

The main objective of the study was determine the loading history and establish the current state of consolidation of Neogene clays, to study their lithological and microstructural properties, and to define their geological-engineering properties. To accomplish this task, series of laboratory and field tests were performed. The tests were made on clays taken from pits excavated for underground stations and tunnels (A-14-A-15) in Warsaw and from 2 borehole cores taken from the Stegny experimental field. The tests showed that: the clays are historically overconsolidated with an OCR ratio of 25-50 and their current state of preconsolidation is OCR = 2-14; their range of clay microstructures, observed for the first time, are matrix-turbulent and turbulent-laminar and there was a clear anisotropy of quantitative parameters of the pore paces, these parameters varying with depth. The engineering-geological characteristics (physical and mechanical properties) of the clays were assessed. The results of the study can be used directly to evaluate the Neogene clays of the Warsaw area for their suitability as a subsoil for engineering projects and indirectly to accomplish the same with other overconsolidated soils, particularly in regard to the study methodologies applied and described.