Browsing by Subject "grain size"

Now showing 1 - 5 of 5

Access status: Open Access ,
Accounting for the random character of nucleation in the modelling of phase transformations in steels
(Wydawnictwa AGH, 2023) Poloczek, Łukasz; Kuziak, Roman; Foryś, Jakub; Szeliga, Danuta; Pietrzyk, Maciej
In our earlier work, a stochastic model of multi-stage deformation at elevated temperatures was developed. The model was applied to calculate histograms of dislocation density and grain size at the onset of phase transformation. The histograms were used as input data for the simulation of phase transitions using the traditional deterministic model. Following this approach, microstructural inhomogeneity was predicted for different cooling conditions. The results obtained, showing the effect of dislocation density and inhomogeneity of austenite grain size on the microstructural inhomogeneity of the final product, can be considered reliable as they are based on material models determined in previous publications and validated experimentally. The aim of the present work was to extend the model by taking into account the stochastic nature of nucleation during phase transitions. The analysis of existing stochastic models of nucleation was performed, and a model for ferritic transformation in steels was proposed. Simulations for constant cooling rates as well as for industrial cooling processes of steel rods were performed. In the latter case, uncertainties in defining the boundary conditions and segregation of elements were also considered. The reduction of the computing costs is an important advantage of the model, which is much faster when compared to full field models with explicit microstructure representation.
Access status: Restricted ,
Geologiczno-inżynierska charakterystyka nadkładu złoża Zakładu Górniczego Lipowica
(Data obrony: 2018-01-29) Majkut, Łukasz
Wydział Geologii, Geofizyki i Ochrony Środowiska
Optymalny wariant zagospodarowania zasobów złoża polega nie tylko na racjonalnym wykorzystaniu kopaliny głównej lecz także jego nadkładu. Efektywne wykorzystanie utworów z nadkładu złoża zależy w zasadniczym stopniu od uwarunkowań geologiczno-inżynierskich. Zastosowanie gruntów nadkładu w rozwiązaniach geotechnicznych, np. do budowy nasypów drogowych, kolejowych lub wałów przeciwpowodziowych wymaga zbadania ich parametrów fizyko-mechanicznych. Oznaczenie właściwości nadkładu jest niezbędne także do tworzenia statecznego zwałowiska. Celem pracy było rozpoznanie i scharakteryzowanie parametrów geologiczno-inżynierskich nadkładu złoża piaskowca cergowskiego w Zakładzie Górniczym Lipowica. W ramach prowadzonych prac wykonano 5 otworów wiertniczych, z których pobrano próbki do badań laboratoryjnych. Oznaczono takie parametry jak: wilgotność naturalną, granice konsystencji, uziarnienie oraz wytrzymałość na ścinanie. Wyniki badań wykazały, że analizowane grunty są względnie jednorodne, posiadają korzystne wartości parametrów fizyko-mechanicznych i mogą zostać wykorzystane w budowlach ziemnych.
Access status: Open Access ,
Grain size measurement using a semi-automatic calculation tool
(Wydawnictwa AGH, 2023) Mernache, Fatah; Sehisseh, Abdelaziz; Amrane, Amina; Hadji, Said; Melhani, Yasmine; Grine, Mohamed; Messai, Lakhdar
This paper focuses on the development of a semi-automatic calculation tool to measure the Mean Linear Intercept (MLI) grain size of ceramics and other materials. The calculation tool was first verified and validated by using a certified micro-ruler and literature microstructures. It was then used to investigate the grain growth of $UO_{2}$ pellets elaborated under different conditions. The tool offers the advantage of accuracy as well as the ability to quantify microstructures obtained with poor image quality. The estimated measurement errors were found to be less than 1 ?m. The developed tool, mainly for the purpose of time-saving, allowed us to follow the microstructure (grain size) evolution of the elaborated $UO_{2}$ fuel with different additives.
Access status: Open Access ,
Influence of cooling rate on the structure and damping properties of the AlSi6Cu4 alloy
(AGH University Press, 2025) Piwowarski, Grzegorz; Ogrodnik, Mateusz
The investigated alloy was cast as a shaft into seven casting molds. Casting molds made of different materials were char acterized by different abilities to conduct heat from the sample. This property significantly influenced the cooling rate of the sample casting from the AlSi6Cu4 alloy. The highest cooling rate was achieved in a steel mold at 25°C and the lowest in a mold made of insulating mass. Different cooling rates significantly influenced the structure of the alloy. Different grain sizes were obtained and the morphology of the microstructure components changed. At the highest cooling rate of 16.63 K·s?1, a grain with an average size of 0.58 mm was obtained. However, in the mold with the lowest cooling rate of 0.36 K·s?1, the average grain size was 3.76 mm. Changes in the structure of the alloy also influenced its damping prop erties. The tested values f the vibration damping coefficient ? indicated that the AlSi6Cu4 alloy cooling with the highest cooling rate has the highest value of damping coefficient. This is influenced by the grain size and shape of the silicon pre cipitates. The refinement structure and fragmented components effectively disperse the vibration wave in the structure of the casting alloy.
Access status: Open Access ,
Microstructure of magnesium alloy AZ31 after low-speed extrusion
(2007) Skubisz, Piotr; Skowronek, Tadeusz; Sińczak, Jan
Direct extrusion of magnesium alloy AZ31 and changes in microstructure resultant from low-speed small-reduction extrusion are presented. The results show possibilities of grain refinement and improvement of mechanical properties associated with limited amount of generated deformation heat in aspect of using as-extruded material as a forging stock.