G. Niewielski

Heat treatment of high manganese type X57MnAl27-5 austenitic steel

In the paper, the influence of heat treatment parameters on microstructure and mechanical properties of high manganese type X57MnAl27-5 austenitic steel was investigated. The as-forged bar with diameter of 15 mm were underwent a saturation process at six different temperatures. The microstructural changes of austenite and the influence of heat treatment on the mechanical properties were considered. The quantitative analysis of austenite phase of the examined steel indicated that the parameters of saturation process resulted in changes of morphology and grain size of austenite. It was revealed that treatment temperature in the range of 950 °C-1100 °C slightly influenced grain size, stress limit and hardness of the investigated steel. Treatment at temperature higher than 1150 °C resulted in the growth of austenite grain size and the decrease of mechanical properties.

High Manganese TWIP Steel - Technological Plasticity and Selected Properties

Over the last few years national as well as international research centres conducting research on the development of high-manganese steels. Some of these materials belong to the group of AHS steels, are characterized by the twinning induced plasticity (TWIP) effect which is a new type of steel possessing together with high strength a great plastic elongation, and an ideal uniform work hardening behavior. It is therefore a good candidate for deep drawing applications in the automobile and railway industry. The article presents the results of researches of TWIP-type austenitic steel in case of determination some of the more important parameters for continuous casting simulation process and the results of tests regarding the influence of strain parameters on sensitivity to plastic forming and deformation strengthening. It has been shown that the researched steel reaches a zero plasticity temperature at 1250°C. The deformation tests indicate its good workability of hot processing within the temperature range of 1100 ÷ 800°C. The relation between yield stress and strain during the hot deformation is typical for the presence of dynamic recrystallization processes. The tested steel has good formability and high mechanical properties, especially when being deformed at a high strain rate. Analysis of the substructure of researched steel was indicate presence of mechanical twinning.

Research of selected properties of two types of high manganese steel wires

The article presents results of tests that aimed at establishing the impact of deformation on properties of wires made of two types of high manganese steels. The deformation process was carried out with the use of a draw bench machine at a speed of 0.5 m min−1. Mechanical properties and structure of strengthened and annealed wires for both steels at different levels of relative reduction in cross-section were determined. Strength of the tested materials was determined in the tensile test, while its hardness was measured with the Vickers hardness test method. Fractographic tests were performed using a scanning electron microscope. It was shown that at the beginning of tensile test, the investigated high manganese steels were characterized by very high plasticity and become stronger as the degree of deformation grows. Surfaces of fractures that were created in the areas where the sample was torn were analyzed. These fractures indicate the presence of transcrystalline ductile fractures.

The influence of thermo-mechanical treatment on the structure and plasticity of FeAl intermetallic phase–base alloy

Alloys based on intermetallic phases from the Fe-Al system they belong to a group of high-temperature creep resisting materials of advantageous physicochemical and mechanical properties at an elevated and high temperature. In general, limitation on the capacity for a broad application of intermetals from the Fe-Al system, e.g. as an alternative to expensive alloy steels of specific properties, is their insufficient plasticity, which is a factor inhibiting further their development as constructional materials. Under this study, research has been conducted on the capacity for forming alloys based on intermetallic phases from the Fe-Al system, via thermo-mechanical processing. In the present work, the possibility of forming Fe-Al-intermetallic-phase-based alloys in thermo-mechanical treatment (TMT) has been studied. After casting and annealing, alloy specimens were subjected to axial-symmetric compression in the Gleeble 3800 simulator in the range of 700–1200 °C at 0.01, 0.1, 1.0, 10 s −1 strain rates. In order to analyze the processes which take place during deformation, the specimens after deformation were intensely cooled with water. Structural examination was carried out using light and electron microscopy. The impact of hot rolling process parameters on the structure of intermetallic-phase-based FeAl alloys and properties has been determined. The results will constitute the basis for modelling the structural changes in FeAl intermetallic alloy.

Complex Flow Stress Model for a Magnesium Alloy AZ31 at Hot Forming

Abstract Compression tests of magnesium alloy Mg-3Al-1Zn (AZ31) at different temperatures and strain rate were made on plastometer Gleeble 3800. Deformation behaviour and particularly shape of stress-strain curves of the alloy AZ31 differ significantly at low and high values of Zener–Hollomon parameter Z. The border between these areas was determined mathematically as Z = 2.9E+13 s–1. While the calculated activation energy Q was for both these areas practically identical (157 or 155 kJ mol–1), mathematical description of coordinates of the peak stress differs considerably. Regression and statistical analysis of experimental data have confirmed unequivocally, that it was impossible to describe by a uniform equation the whole set of data (i.e. traditional stress-strain curves, as well as those with atypical initial stage, given by the massive twinning). Thats why two mathematical models were developed enabling prediction of the flow stress of investigated magnesium alloy in dependence on temperature, strain and strain rate, with inclusion of the influence of dynamic recrystallisation.

The Influence of Deformation Conditions on Structure of Fe-Al Intermetallic Phase ‒ Based Alloys

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.

The impact of compression with oscillatory torsion on the structure change in copper

The influence of compression with oscillatory torsion on the copper structure and force parameters are presented. The compression with oscillatory torsion method, developed in the Faculty of Materials Science and Metallurgy at the Silesian University of Technology, is used to achieve severe plastic deformation resulting in homogeneous ultrafine-grained structure of metals. The deformation resistance of copper for various torsion frequency and compression rate is presented. The results of microstructural observations by using LM (light microscope) and TEM (Transmission Electron Microscope) technique are displayed as well. The geometrical parameters of structure elements and their misorientation angles were characterized by using TEM method. Application of compression with oscillatory torsion was found to cause a remarkable decrease of deformation resistance as compared to compression without torsion. Plastic flow localized in shear bands was observed. Structures with large misorientation occur in microbands areas. The banded structure formed during compression with oscillatory torsion consists of well-formed, elongated subgrains.

Influence of the Thermo-Mechanical Treatment on the Properties and Microstructure of High Manganese Austenitic-Ferritic Steel

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.

Welding of Steel with High Manganese and Aluminum Content

The paper presents results of tests of mechanical properties, hardness measurements, macro-and microstructures of welded joints austenitic and austenitic-ferritic steel with high manganese and aluminium content meant for automotive industry. Tests were conducted on flat sheets made of steel X20MnAl18-3 and X55MnAl25-5. Tested welded joints were ruptured in tensile strength test in all cases inside the weld which is connected with lower resistance to stretching of welded joints in comparison with resistance of joined steels. Resistance to stretching of tested samples, regardless of the method of welding, is on a similar level.

Electro-chemical monitoring of static recrystallization

The electro-chemical potentio-kinetic method has proved to be a sensitive technique for monitoring of static recrystallization in austenitic steel AISI 304 after its cold forming and annealing. Results obtained in this manner are in very good conformity with the results of metallographic and X-ray analysis, as well as with the measured values of hardness. Corrosion current density appeared to be a suitable criterion for evaluation of development of relaxation processes.