Papers by Author: Magdalena Jabłońska

Abstract: The article presents the dynamic mechanical properties of two types of high manganese austenitic steels. The investigation were carried out for the wide range of strain rates from 1×10^-4s^-1 up to 4×10³s^-1 using servo-hydraulic testing machine and Hopkinson bar for the quasi-static and dynamic loading regime, respectively. The mechanical properties at different strain rates as well as the SEA indicator calculated were carried out on the base of the results of impact tests. In the next step, the microstructure of the steel after different deformation rate was observed and analyzed by light microscope in order to disclose a TWIP effect.

Abstract: The purpose of carried out examination was to determine the effect of solution heat treatment on the structure and corrosion resistance of the ZnAl40Cu3 alloy in the "acid rain" environment. The scope of the test included Brinell hardness tests, structural tests and galvanostatic and potentiodynamic tests. The examination showed that the maximum hardness of the sample after solution heat treatment obtain after 10 h of solutionizing. It has been shown that the solutionizing increases the corrosion resistance. The corrosion resistance was greater, when the longer was the time of solutionizing.

Abstract: The purpose of the examination was to determine the corrosion resistance of ZnAl40Cu(1-2)Ti(1-2) alloys in an "acid rain". Subject of test were ZnAl40Cu2Ti, ZnAl40Ti2Cu1.5Ti1.5 and ZnAl40Ti2Cu alloys. The scope of the test included galvanostatic, potentiodynamic tests and examination of the surface of the samples after corrosion. It was found, that the ZnAl40Cu2Ti alloy is characterized by the highest corrosion resistance among the tested alloys. Tests have shown that with a decrease in copper content in the tested alloys decreases corrosion resistance. It was also found that the corrosion of alloys tested in an "acid rain" is local.

Abstract: Current research in the field of iron aluminides are directed towards to understand the structural phenomena occurring during plastic deformation of these alloys. The obtained results of the study and collected informations will be used to determine the description of the structural changes taking place during hot deformation of Fe ̶Al alloys. The article presents the results of the study of the alloy FeAl28Cr5 deformed by hot torsion in temperature range of 800÷1100^°C and a strain rate of 0.1 s^-1. The analysis of the structure of the alloy FeAl28Cr5 allowed to reveal changes caused by dynamic processes of deformation. The results of torsion tests show the possibility to obtain a fine-grained structure with of parameters of the processes (T=1000^°C, 1100^°C) and strain of ε=40. After deformation at strain of (ε=40) the structure consists of fine grains with a misorientation angle higher than 15^°, and the average grain size diameter D=28.5 micrometers. Deformation at a temperature of T=1000^°C and 1100^°C is accompanied by superplastic flow effect.

Abstract: In the paper, results of impact bending tests of a high-manganese steel of X30MnAlSi26-4-3 grade are presented. The tests were carried out using a flywheel machine, suitable for dynamic tensile tests and impact bending tests in the range of linear velocity of the forcing element from 5 ÷ 40 m/s. The obtained test results were compared with the results of impact resistance of the studied steel determined using Charpy machine. Structural investigations were carried out using light microscope and scanning transmission electron microscopy. Creating a mechanical twins at different strain rates was analyzed. The surfaces of fractures formed in the break point during bending tests were analyzed, and they indicate a presence of mixed transcrystalline fractures with a predominance of plastic fractures. Substructure studies revealed the presence of mechanical twinning induced in a high strain rate for the X30MnAlSi26-4-3 steel.

Abstract: Institute of Materials Science at Silesian University of Technology since 6 years conducts researches to learn about the new dedicated for automotive, railway and military industries. Some of these materials belong to the group of AHS steels, characterized by the twinning induced plasticity (TWIP) effect. It is a new type of steel possessing both a high strength and a great plastic elongation, and an ideal uniform work hardening behaviour. It is therefore a good candidate for deep drawing applications in the automobile and railway industries. In the paper the of the three grades of high-manganese steels of was studied in 3.5% NaCl solution and in an “acid rain” solution with pH=3.5 environments using polarization experiments. The results of corrosion tests and analysis of show that a higher polarisation resistance and lower values of corrosion current density are observed for all studied steels in 3.5% NaCl solution. Spontaneous passivation ability has been shown only for one grade of high-manganese steel in 3.5% NaCl.

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: Characterization of microstructure of silicide coatings obtained during diffusion process of pack cementation type was showed in this article. The basic materials were pure Mo sheet and TZM molybdenum alloys as well. The coatings were deposited in out of pack process with three different times of exposure. The temperature of deposition process was constant. In first step the phases compositions of coatings was described by XRD analysis. In each cases the MoSi₂ phase was obtained on top surface of the coatings. The morphology of the coatings was very similar as well. All types of coatings were characterized by network of cracks on top surface of the coatings. There was no influence of depositions time on phases constituent and coatings topography. LM and SEM analysis revealed that internal coatings morphology was very similar in all cases. Basic differences was related to the thickness of coatings. All coatings were good quality without deep cracks. Microstructure was a columnar-like type without pores and voids.

Abstract: In last ten years, leading research centers have been directed to the development of high-Mn steels for manufacturing of parts for automotive industry. The discussed steels with different values of Mn, Al, and Si addition have a medium value of EBU. They usually demonstrate a dominant stress mechanism like twinning induced plasticity TWIP. During the plastic deformation, they may demonstrate a two stress mechanisms like sliding and twinning. The paper presents the results of an analysis of the substructure of high manganese steel after deformation by cold rolling in the context of dominant stress mechanism. The substructure was analyzed by scanning transmission electron microscopy. In the steels, close weaves of dislocations, dislocations tangles, twins and microtwins were observed. It was revealed that the detailed analysis of substructure of the investigated steels after cold deformation could be helpful in determination of the dominant stress mechanism. The obtained results may be used for development of these steels and their plastic deformation models.