Entity

Time filter

Source Type


Gzyl M.,University of Strathclyde | Rosochowski A.,University of Strathclyde | Boczkal S.,Institute of Non Ferrous Metals in Gliwice | Olejnik L.,Warsaw University of Technology
Materials Science and Engineering A | Year: 2015

Mechanical properties of AZ31B magnesium alloy were modified in this work by various processing routes of incremental equal channel angular pressing (I-ECAP) followed by heat treatment. Possible strategies for improving ductility and strength of the alloy were investigated. Processing by routes A and BC showed that texture plays predominant role in controlling mechanical properties at room temperature. Four passes of I-ECAP by route C followed by annealing enhanced ductility up to 0.35 of true strain. It was found that tensile twinning was important in accommodating strain during tensile testing, which resulted in a very good hardening behaviour. The yield strength was improved to 300MPa by refining grain size to 0.8μm in I-ECAP at 150°C. The obtained structure and properties were shown to be stable up to 150°C. True strain at fracture was increased to 0.2 after annealing at 150°C without lowering strength. © 2015 The Authors. Source


Sulima I.,Pedagogical University of Cracow | Boczkal S.,Institute of Non Ferrous Metals in Gliwice | Jaworska L.,Pedagogical University of Cracow
Materials Characterization | Year: 2016

Steel-8TiB2 composites were produced by two new sintering techniques, i.e. Spark Plasma Sintering (SPS) and High Pressure-High Temperature (HP-HT) sintering. This study discusses the impact of these sintering methods on the microstructure of steel composites reinforced with TiB2 particles. Scanning electron microscopy (SEM), wavelength dispersive spectroscopy (WDS), X-ray diffraction, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were used to analyze the microstructure evolution in steel matrix composites. The results of microscopic examinations revealed a close relationship between the composite microstructure and the methods and conditions of sintering. Substantial differences were observed in the grain size of materials sintered by HP-HT and SPS. It has been demonstrated that the composites sintered by HP-HT tend to form a chromium-iron-nickel phase in the steel matrix. In contrast, the microstructure of the composites sintered by SPS is characterized by the presence of complex borides and chromium-iron phase. © 2016 Elsevier Inc. Source


Paclawski K.,AGH University of Science and Technology | Piwowonska J.,Institute of Non Ferrous Metals in Gliwice
Archives of Metallurgy and Materials | Year: 2014

In this work, spectrophotometric studies on the kinetics and mechanism of the reaction between [PtCl6]2- complex ions and sodium thiosulfate, in neutral (pH = 7) and alkaline (p = 12) solution, were carried out. Applying different conditions, the influence of initial concentrations of reductant and platinum(IV) complex ions as well as the influence of temperature and ionic strength on the rate constant, was experimentally determined. From the obtained results, the molecularity, the order and the value of enthalpy and entropy of activation of the reaction, were experimentally determined. It was found that in both cases the reduction reaction is relatively slow and in the studied conditions the second-order rate constant changes from 2.92·10-2 to 0.40 M-1·s-1 at pH = 7, and from 3.84·10-2 to 1.55 M-1 s-1 at pH = 12. Additionally, depending on the pH, different mechanism of the reaction is present. However, regardless on the studied system the only platinum(II) chloride complex ions are the final product of the redox reaction. © 2014, Committee of Metallurgy. All rights reserved. Source


Paclawski K.,AGH University of Science and Technology | Piwowonska J.,Institute of Non Ferrous Metals in Gliwice
Archives of Metallurgy and Materials | Year: 2014

In this work, spectrophotometric studies of the kinetics and mechanism of reaction between [PtCl6]2- complex ions and sodium thiosulfate, were carried out. The influence of different conditions, such as: initial concentrations of reductant and platinum(IV) complex ions, ionic strength, pH and temperature on the rate constant, was experimentally determined. From the obtained results, the molecularity of the first elementary step, value of the enthalpy and entropy of activation in Eyring equation as well as corresponding rate equation, were experimentally determined. It was found that the reaction is relatively slow and leads to the S, Pt and PtS colloids formation. The best conditions for solid phase formation containing Pt are at pH = 5. © 2014, Committee of Metallurgy. All rights reserved. Source


Gzyl M.,University of Strathclyde | Rosochowski A.,University of Strathclyde | Boczkal S.,Institute of Non Ferrous Metals in Gliwice | Qarni M.J.,University of Strathclyde
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2015

Magnesium alloys are very promising materials for weight-saving structural applications due to their low density, comparing to other metals and alloys currently used. However, they usually suffer from a limited formability at room temperature and low strength. In order to overcome those issues, processes of severe plastic deformation (SPD) can be utilized to improve mechanical properties, but processing parameters need to be selected with care to avoid fracture, very often observed for those alloys during forming. In the current work, the AZ31B magnesium alloy was subjected to SPD by incremental equal-channel angular pressing (I-ECAP) at temperatures varying from 398 K to 525 K (125 °C to 250 °C) to determine the window of allowable processing parameters. The effects of initial grain size and billet rotation scheme on the occurrence of fracture during I-ECAP were investigated. The initial grain size ranged from 1.5 to 40 µm and the I-ECAP routes tested were A, BC, and C. Microstructures of the processed billets were characterized before and after I-ECAP. It was found that a fine-grained and homogenous microstructure was required to avoid fracture at low temperatures. Strain localization arising from a stress relaxation within recrystallized regions, namely twins and fine-grained zones, was shown to be responsible for the generation of microcracks. Based on the I-ECAP experiments and available literature data for ECAP, a power law between the initial grain size and processing conditions, described by a Zener–Hollomon parameter, has been proposed. Finally, processing by various routes at 473 K (200 °C) revealed that route A was less prone to fracture than routes BC and C. © 2015, The Minerals, Metals & Materials Society and ASM International. Source

Discover hidden collaborations