Papers by Author: Dariusz Kuc

Abstract: The article presents the results of tests which are connected with possibilities of forming the magnesium alloys. Research was conducted on the basis of the plastic forming test with the use of KOBO method – cold forming. Materials for tests were ingots from magnesium alloys and the results of tests were the achieved flat bars. Microstructure tests were conducted with the use of optical and electron microscopes. The mechanical properties of the tested materials are presented in the paper together with the advantages of the achieved alloys. It was possible to determine the possible further research directions connected with this material.

Abstract: New generation high-strength austenitic and austenitic-ferritic manganese steels represent a valid potential in applications for components in the automotive and railway industry due to the perfect combination of high mechanical properties and formability. Applying this new steels with their combination of properties allows for reduce the weight of vehicles by the use reduced cross-section components and thus to reduce fuel consumption. The development and implementation of industrial production and the use as construction materials such interesting and promising steel is conditioned to improve their casting properties and susceptibility to deformation during thermomechanical processes conditions. In this work, applied an new high manganese austenitic-ferritic steel for analysis the influence of the cooling medium in thermomechanical processes on the mechanical properties and structure of researched steel. The steel was hot rolled with finish temperature 900°C and next cooled with different conditions. Change the cooling conditions effect on the changes in the microstructure of the tested steel, observed grain refinement of austenite and ferrite morphology change. Also are changing the mechanical characteristics of the tested steel.

Abstract: In recent years, the leading scientific centres focus their research on improvement of mechanical properties of steels used for car manufacturing. These steels belong to a so-called 2^nd generation of steels showing above-the-average plasticity while maintaining high strength. Thanks to these properties, they may be used successfully in automotive, armaments or railway industries for elements absorbing energy of a collision and ensuring high rigidity of a structure owing to their resistance to breaking. These steels are called TWIP (Twinning Induced Plasticity) steels based on their hardening mechanism. In this paper, results of studies on the influence of parameters of thermo-plastic deformation on selected properties and structure of an X45MnAl20-3V austenitic steel showing the TWIP effect are presented. Moreover, an analysis of influence of the deformation on the structure of the studied steel in tensile tests has been carried out. The studied steel was manufactured by classic casting to a concast mould, obtaining ingots with dimensions of 100×100 mm, then subjected to rolling in 4 roll passes to a final thickness of 12 mm and 3 mm. The finish-rolling temperature was 950°C and the sheets were cooled in 2 media, i.e. in air and in water. It was confirmed that the studied steel belongs to the TWIP group of steels, with mechanical twinning being the prevailing process of hardening during deformation.

Abstract: The article presents the results of tests connected with influence of strain parameters on the susceptibility to hot working of magnesium lithium alloys with lithium content of 7.5% mass. Plasticity tests were conducted in compression test from room temperature up to 400°C with strain rate of 0.1s^-1. Conducted tests allowed for determination of susceptibility of magnesium alloys with different lithium content to hot working. The results were compared with typical alloy AZ31. The results of influence of deformation temperature on the microstructure of tested alloys are also presented in this paper.

Abstract: Department of Materials Science at Silesian University of Technology since 10 years conducts researches to learn about the structural phenomena which occur during hot plastic treatment which are aimed at elaboration of a technology of heat and plastic treatment of selected alloys from Al-Fe diagram. The iron aluminides have been among the most widely studied intermetallics because their low cost, low density, good wear oxidation and corrosion resistance, to create wide prospects for their industrial applications, for components of machines working at a high temperature and in corrosive environment. The problem limiting their application is low plasticity and brittle cracking susceptibility. Consequently, the research of intermetallic-phase based alloys focuses on their plasticity. For the development of thermo-plastic treatment technology, it is necessary to determine internal variables describing the structure of an alloys being deformed is the inhomogeneity, grain size, as well as the grains misorientation angles and texture. The paper presents the course of structural changes of Fe-38Al with Zr, B Mo and C additions under the influence of hot plastic deformation with application of a few different temperatures of the process with given speed of deformation. For the structure and substructure investigations were used a light microscopy and transmission electron microscopy.

Abstract: The effect of cold rolling and annealing treatments in two temperatures, 800°C and 900°C on texture formation in duplex steel (X60MnAl30-9) was examined. Texture measurements were carried out using X-ray diffraction and Schulz reflection technique. The mechanical properties i. e. 0.2% proof stress, ultimate tensile strength and elongation were measured for each experimental conditions. It was found that ferrite was characterized by the orientations of a fibre which could be found in cold rolling state and also after the annealing in both temperatures. The weak orientations close to g fibre were observed after the annealing. The cold rolling texture of austenite was a typical texture of cold rolled fcc metals. No significant changes in texture of austenite after the annealing treatments were found.

Abstract: The paper presents a model of microstructure changes elaborated for magnesium alloy type AZ31. In previous papers, the function of flow stress was defined on the basis of uniaxial hot compression tests. On the basis of marked relaxation curves and quantitative tests of structure the softening indicators were defined together with elaboration of equations which describe the changes in the grain size. Marked coefficients of equations were introduced in the code of simulation program. Calculations were conducted for given temperature values from 450 ÷ 250°C and strain rate from 0.01 to 10 s-1, which correspond with rolling temperature range of this alloy. Prepared model will allow the proper choice of parameters in hot rolling process of this alloy to achieve the assumed microstructure.

Abstract: The article presents the results of tests connected with the influence of strain parameters on the change of flow stress and microstructure of magnesium alloy AZ61 (symbol according to ASTM norms). Test of uniaxial hot compression were conducted in temperature range from 250 to 400°C and the strain speed from 0.01 to 1 s-1. Analysis of plastometric tests and microstructure observation allowed to establish which mechanism - slip or twinning – is dominant in particular conditions of shaping AZ61 alloy. Achieved results were compared with previous results achieved for AZ31 alloy type with lower content of aluminium.

Abstract: The paper is focused on application of multi-scale 2D CAFE method. CAFE approach consists of Cellular Automata (CA) model of microstructure development and the thermal-mechanical finite element (FE) code. Dynamic recrystallization phenomenon is taken into account in 2D CA model which takes advantage of explicit representation of microstructure, including individual grains and grain boundaries. Flow stress is the main material parameter in mechanical part of FE and is calculated on the basis of average dislocation density obtained from CA model. The results attained from the CAFE model were validated with the experimental data for austenitic steel X3CrNi18-9. The samples were subjected to axisymmetrical hot compression test. Compression forces were recorded during the tests and flow stresses were determined using inverse method. Light microscopy and EBSD analyses were performed for the initial and final microstructures of the samples.

Abstract: The major problem restricting universal employment of intermetallic phase base alloy is their low plasticity which leads to hampering their development as construction materials. The following work concentrates on the analysis of microstructure and plasticity of ordered Fe3Al (D03) and FeAl (B2) during hot plastic deformation process.. The microstructure analyses applying optical electron microscopy and EBSD method have revealed the structure reconstruction processes occurring in Fe3Al and FeAl alloys. It has been shown that different mechanisms of the structural changes ensue from the thermal plastic strain in the investigated alloys, which influences their technological plasticity.