J. Mazurkiewicz

2.10 – Structure and Mechanical Properties of High-Manganese Steels

This chapter presents results from investigations about high-manganese austenitic steels, which have gained increasing importance over the recent two decades. Intense research into this group of steels indicates the need for employing them in the global automotive sector, especially for constructional components of cars absorbing impact energy in road collisions. The examples of extensive research over this group of high-manganese austenitic steels have been pursued by the authors at the Division of Materials Processing Technology, Management and Computer Techniques in Materials Science, the Institute of Engineering Materials and Biomaterials of the Silesian University of Technology, Gliwice, Poland. The essence of the research concerns the designing of thermo-mechanical processing of selected high-manganese austenitic steels with carefully selected but diversified chemical composition in order to refine their structure and improve mechanical properties. Thermo-mechanical processing was performed using a thermo-mechanical simulator DSI (Dynamic System Inc.) Gleeble 3800. The results of the investigations performed with the DSI simulator allowed to design different variants of hot rolling consisting of several stages for the investigated high-manganese austenitic steels. Different processes controlling the curve of strain hardening could be used by applying the varied conditions of thermo-mechanical processing, and especially a diversified degree of deformation and isothermal heat treatment after finishing plastic working, such as dynamic recovery, dynamic recrystallization, and static recrystallization.

Selective metallization of solar cells

Purpose – This paper aims to present the possibility of the technology of chemical metallization for the production of contact of photovoltaic cells. The developed technology allows you to perform low-cost contacts in any form. Design/methodology/approach – The study used a multi- and monocrystalline silicon plates. On the surface of the plates, the contact by the electroless metallization was made. After metallization stage, annealing process in a temperature range of 100-700°C was conducted to obtain ohmic contact in a semiconductor material. Subsequently, the electrical parameters of obtained structures were measured. Therefore, trial soldering was made, which demonstrated that the layer is fully soldered. Findings – Optimal parameters of the metallization bath was specified. The equations RS = f (metallization time), RS = f (temperature of annealing) and C-V characteristics were determined. As a result of conducted research, it has been stated that the most appropriate way leading to the production of...

Mechanical Properties of High-Manganese Austenitic TWIP-Type Steel

Taking into consideration increased quantity of accessories used in modern cars, decreasing car’s weight can be achieved solely by optimization of sections of sheets used for bearing and reinforcing elements as well as for body panelling parts of a car. Application of sheets with lower thickness requires using sheets with higher mechanical properties, however keeping adequate formability. The goal of structural elements such as frontal frame side members, bumpers and the others is to take over the energy of an impact. Therefore, steels that are used for these parts should be characterized by high value of UTS and UEl, proving the ability of energy absorption. Among the wide variety of recently developed steels, high-manganese austenitic steels with low stacking faulty energy are particularly promising, especially when mechanical twinning occurs. Beneficial combination of high strength and ductile properties of these steels depends on structural processes taking place during cold plastic deformation, which are a derivative of SFE of austenite, dependent, in turn on the chemical composition of steel and deformation temperature. High-manganese austenitic steels in effect of application of proper heat treatment or thermo-mechanical treatment can be characterized by different structure assuring the advantageous connection of strength and plasticity properties. Proper determinant of these properties can be plastic deformation energy supply determined by integral over surface of cold plastic deformation curve. Obtaining of high strength properties with retaining the high plasticity has significant influence for the development of high-manganese steel groups and their significance for the development of materials engineering.

Electrical characterization of 1D SnO 2 nanowires

In this study, a method to identify the impedance of the sample composed of SnO2 nanowires (NWs) has been presented. The studied sensor structures were based on one-dimensional (1D) SnO2 NWs grown by thermal deposition on silicon substrate. The topography of SnO2 NWs was investigated by means of scanning electron microscopy (SEM). The results of qualitative and quantitative analysis in selected microregion have been presented. Furthermore, the electrical properties of the NWs were measured. The base of the measurement comprised impedance spectroscopy, Padé data approximation restrained by passivity condition. This study demonstrates that it is possible to separate the characteristic parameters for various transport phenomena in the NW.

Effect of strain deformation rates on forming the structure and mechanical properties of high-manganese austenitic TWIP steels

Abstract The aim of this paper is to determine the influence of strain rate on mechanical properties and structure of high-Mn austenitic TWIP steels. Deformation rates in a range from 0.001 to 1000 s−1 have a significant effect on forming the structure and mechanical properties of high-manganese austenitic TWIP-type steels. TWIP steels not only show excellent strength, but also have excellent formability due to twinning, thereby leading to excellent combination of strength, ductility and formability over conventional dual phase steels or transformation-induced plasticity steels. Also the strain energy per unit volume of advanced high-Mn TWIP steels containing Mn, Al, SI and some of that steels with Nb and Ti microadditions with various structures after their heat- and thermomechanical treatments increases considerably in dynamic conditions. The microstructure of investigated steels was determined in metallographic investigations using light, scanning and high-resolution transmission electron microscopes. Results obtained in static and dynamic conditions for newly developed high-manganese austenitic steels indicate the possibility and purposefulness of their employment for constructional elements of vehicles, especially of the passenger cars to take advantage of the significant growth of their strain energy per unit volume which guarantee reserve of plasticity in the zones of controlled energy absorption during possible collision resulting from the activation of twinning induced by cold working, which may result in significant growth of the passive safety of these vehicles’ passengers.

Electrical and optical properties of spin-coated SnO2 nanofilms

SnO2 nanocrystalline thin films have been deposited on oxidized silicon substrates by spin-coating from a precursor solution, followed by slow thermal annealing in oxygen atmosphere at different temperatures (500 to 900 °C). The precursor solution consisted of 1.0 to 2.0 M SnCl4·5H2O in isopropanol. It was shown that the concentration of the precursor solution, annealing temperature and heating rate had a significant effect on the structural, optical and electrical properties of the studied thin films. The topography of SnO2 thin films was examined by scanning electron microscopy (SEM). Furthermore, as-deposited films were characterized by X-ray diffraction (XRD), UV-Vis and impedance spectroscopy.