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Fatigue behaviour of AZ31 and AZ61 magnesium alloys after corrosion degradation
Horynová, Miroslava ; Vojtěch, Dalibor (referee) ; Obrtlík, Karel (referee) ; Podrábský, Tomáš (advisor)
Dissertation thesis is focused on evaluation of influence of exposure in 5% salt fog on fatigue behavior of AZ31 and AZ61 magnesium alloy fabricated by squeeze casting method. Microstructure and mechanical properties of experimental materials have been evaluated. The AZ61 alloy was solution heat treated after prior optimization of the heat treatment process based on microstructural characteristics and mechanical properties. Depths of corrosion damage, corrosion rate and mechanism of corrosion of all three experimental alloys have been evaluated. Influence of prior corrosion exposure for 480 and 1000 hours on fatigue behavior of experimental materials was evaluated. Obtained data were compared with data obtained using smooth test specimens. Fractographic analysis was carried out on both smooth and precorroded specimens. Furthermore, influence of aluminium on corrosion and fatigue behavior of tested alloys was defined.
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Structure and Properties of Selected Magnesium Cast Alloys
Svozil, Libor ; Pacal, Bohumil (referee) ; Podrábský, Tomáš (advisor)
Microstructure and mechanical properties of AZ91 magnesium alloy after die cast (casting under pressure) and squeeze casting were comparated. The compare of incident phases, their microhardness, gas bubbles in the alloy, hardness and other mechanical properties of alloy are included in this work. For compare has been used a light microscopy, tensile test, hardness and microhardness measurements, image analysis and scaning electron microscopy.
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Low Cycle Fatigue of Magnesium Alloy AZ91
Julišová, Martina ; Podrábský, Tomáš (referee) ; Juliš, Martin (advisor)
The objective of the present study is to investigate the fatigue characteristics of cast magnesium alloy AZ91 after low–cycle fatigue tests at the indoor temperature. Squeeze casting specimens in both non–thermal treatment cast state and in solution annealing state were used as the experimental materials. Cyclic hardening/softening and fatigue life curves were obtained from the tests varying according to the way of thermal treatment. This bachelor thesis includes also fracture tests of specimens. Light microscopy and scanning electron microscopy were used for the investigation.
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Modern trends of production Al-based castings
Kovář, Jan ; Kaňa, Václav (referee) ; Krutiš, Vladimír (advisor)
This bachelor thesis is a recherche discussing new methods of the production al-alloy castings, which are mainly developed for the needs of automotive and airspace industry. The described methods are semi-solid casting and metal-matrix composites as the approaches of slurry production and squeeze casting and V-process as the approaches of casting. Further are described SLS, SLM and MJF methods of rapid prototyping and the structure of SLMed AlSi9Cu3 alloy is observed.
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Evaluation of electrochemical characteristics of AZ61 magnesium alloy processed by squeeze casting
Pikner, Jan ; Hadzima, Branislav (referee) ; Fintová, Stanislava (advisor)
Bachelor thesis deals with the characterization of electrochemical corrosion properties of AZ61 magnesium alloy prepared by squeeze casting method. The theoretical part of the work focuses on properties of AZ61 alloy, influence of alloying elements on magnesium alloys and corrosion. The practical part of the work deals with electrochemical characteristics of AZ61 alloy with different surface condition in of 0.1 M NaCl solution. Corrosion potential (Ekor) and corrosion current density (ikor) were determined by potentiodynamic test. Polarisation resistance was determined by electrochemical impedance spectroscopy. Based on the measured results was discussed the influence of production, chemical composition, structure and surface treatment (grinding and polishing) on corrosion characteristics of the alloy.
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Fatigue behaviour of AZ31 and AZ61 magnesium alloys after corrosion degradation
Horynová, Miroslava ; Vojtěch, Dalibor (referee) ; Obrtlík, Karel (referee) ; Podrábský, Tomáš (advisor)
Dissertation thesis is focused on evaluation of influence of exposure in 5% salt fog on fatigue behavior of AZ31 and AZ61 magnesium alloy fabricated by squeeze casting method. Microstructure and mechanical properties of experimental materials have been evaluated. The AZ61 alloy was solution heat treated after prior optimization of the heat treatment process based on microstructural characteristics and mechanical properties. Depths of corrosion damage, corrosion rate and mechanism of corrosion of all three experimental alloys have been evaluated. Influence of prior corrosion exposure for 480 and 1000 hours on fatigue behavior of experimental materials was evaluated. Obtained data were compared with data obtained using smooth test specimens. Fractographic analysis was carried out on both smooth and precorroded specimens. Furthermore, influence of aluminium on corrosion and fatigue behavior of tested alloys was defined.
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Structure and properties of magnesium alloys Mg-Ca-Zn
Hlavnička, Jiří ; Pacal, Bohumil (referee) ; Doležal, Pavel (advisor)
This master’s thesis deals with design and preparation of a new biodegradable magnesium alloy based on Mg-Ca-Zn. Based on information from literature, the Mg-3Zn-2Ca alloy was designed. The base material was produced by gravity casting and the evaluation in the as-cast and heat treated state was performed. For preparation of the experimental material, following methods were designed: squeeze casting, hot rolling and the ECAP. During preparation by hot rolling, no optimal conditions were found and significant cracks occurred in both as-cast and heat treated material. In the case of experimental material, prepared by the ECAP method with back-pressure, better combination of stress-strain properties was observed. Also the squeeze casting method showed improvement; especially the amount of casting defects was eliminated. The evaluation of microstructure and mechanical properties was performed by the light and scanning electron microscopy, RTG phase analysis and the tensile and compression tests.
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Fatigue properties of magnesium alloy AZ31 after corrosion degradation
Horynová, Miroslava ; Lukáč, Pavel (referee) ; Doležal, Pavel (advisor)
The present study is focussed on assessment of cyclic deformation response and fatigue behaviour of bare and precorroded AZ31 magnesium alloys. Corrosion degradation was carried out in a salt spray fog (5% solution of sodium chloride) for 480 and 1000 hrs. Microstructure, mechanical properties, low- and high-cycle fatigue behaviour of experimental material in as-cast condition has been evaluated. Furthermore, the corrosion behaviour of material has been investigated. The fatigue tests have been performed using precorroded specimens to assess influence of corrosion degradation on cyclic deformation response and on low- and high-cycle fatigue behaviour. Influence of local corrosion degradation on initiation of fatigue cracks has been studied.
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Fatigue properties of AZ61 magnesium alloy
Provazníková, Andrea ; Juliš, Martin (referee) ; Pantělejev, Libor (advisor)
This master’s thesis is dealing with low-fatigue behavior of magnesium alloy AZ61, prepared via squeeze casting method. The main aim of this work was to obtain the basic mechanical properties as well as the low cycle fatigue data. Additional metallographical evaluation of microstructure and fractographical analysis after fatigue tests was made.
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