Thesis (Selection of subject)Thesis (Selection of subject)(version: 307)
Assignment details
  
Study of novel magnesium alloys with controlled microstructure and texture
Thesis title in Czech: Studium nových slitin na bázi Mg s řízenou mikrostrukturou a texturou
Thesis title in English: Study of novel magnesium alloys with controlled microstructure and texture
Key words: hořčíkové slitiny, mikrostruktura, mechanické vlastnosti
English key words: magnesium alloys, microstructure, mechanical properties
Academic year of topic announcement: 2016/2017
Type of assignment: rigorosum thesis
Thesis language: angličtina
Department: Department of Condensed Matter Physics (32-KFKL)
Supervisor: doc. Ing. Patrik Dobroň, Ph.D.
Author: hidden - assigned and confirmed by the Study Dept.
Date of registration: 26.09.2017
Date of assignment: 26.09.2017
Confirmed by Study dept. on: 26.09.2017
Date and time of defence: 24.11.2017 00:00
Date of electronic submission:27.09.2017
Date of submission of printed version:26.09.2017
Date of proceeded defence: 24.11.2017
Guidelines
Současný materiálový výzkum věnuje velkou pozornost lehkým konstrukčním slitinám. Vysoké nároky kladené na fyzikální (zejména teplotní) a mechanické vlastnosti, a stejně tak na strukturní stabilitu těchto materiálů vedou k rozvoji nových technologií přípravy. Vzhledem k rostoucí složitosti těchto materiálů není design nových materiálů možný bez důkladného fyzikálního výzkumu.
V navrhované práci se zaměříme na studium vlastností nových slitin na bázi hořčíku (typu AZ s obsahem Al a Zn), obsahujících další minoritní příměsi, jako jsou Mn, Ca, Ce a Zr, a vyznačujících se řízenou texturou danou způsobem přípravy. Zaměříme se na studium vlivu příměsí a textury na mechanické vlastnosti a mikrostrukturní stabilitu. Z experimentálních metod budeme používat zejména měření mechanických vlastností v kombinaci s akustickou emisí. K tomu pak budou prováděna studia struktury a mikrostruktury difrakčními a mikroskopickými metodami.
Práce je podporována dlouhodobým kontraktem o spolupráci mezi UK MFF a Helmholz-Zentrum Geesthacht. Experimentální část práce bude zčásti vykonána na partnerském pracovišti Helmholz-Zentrum Geesthacht.
References
[1] Bohlen, J., Chmelík, F., Dobroň, P., Letzig, D., Kaiser, F., Lukáč, P., Kainer, K.U.: Orientation Effects on Acoustic Emission during Tensile Deformation of Hot Rolled Magnesium Alloy AZ31, J. Alloys and Compounds 378 (2004) 207 – 213.
[2] Dobroň, P., Ph.D. thesis, (2007).
[3] Bohlen, J., Dobroň, P., Hantzsche, K., Letzig, D., Chmelík, F., Kainer, K.U.: Acoustic Emission Study of the Deformation Behaviour of Magnesium Sheets, Int. J. Mater. Res. 100/6 (2009) 790 – 795.
Preliminary scope of work in English
Magnesium and its alloys have an hcp lattice structure which leads to two major effects regarding the properties of wrought magnesium components. On the one hand, the lattice structure limits the number of possible active deformation mechanisms due to its low symmetry. It therefore limits the formability of magnesium structural parts. On the other hand, this lattice structure leads to a significant orientation dependence of properties, i.e. the anisotropy of mechanical properties as well as an asymmetry of the mechanical properties in tension and compression testing. This may also be enhanced due to the formation of distinctive textures during severe plastic deformation as occurs during processes such as rolling, extrusion or forging.
The objective of this study is to understand better the nature of the deformation mechanisms that are active during deformation of various magnesium alloys. Texture-free samples as well as differently textured samples will be analysed using typical mechanical testing methods. Pure magnesium will be investigated and compared first with binary alloys where e.g. Al, Zn, Mn, Ce, Ca are used as alloying elements.
Acoustic emission (AE) which stems from transient elastic waves generated within the material due to sudden irreversible structural changes such as dislocation motion and twinning will be used to yield information on the role of the active deformation modes during deformation and with respect to the texture of the materials.

The signals that occur during testing will be analysed with respect to their original sources, i.e. dislocation glide events or twins. The effect of alloying elements on the activity of these deformation modes will be studied and analysed with respect to the effect of alloying elements and testing temperature. These investigations will be accompanied by texture measurements as well as electron microscopy.

The project is a joint activity between the Department of Physics of Materials at Charles University (CZ) and the Magnesium Innovation Centre MagIC at Helmholz-Zentrum Geesthacht (D). Applicants should be able to speak and write in English fluently. Skills in the German language would be welcome but not mandatory.
 
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