|
| |
|
| |
|
|
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.
|
|
| |
|
| |
|
|
Effect of hyaluronic acid on the corrosion of AZ31 magnesium alloy
Holubářová, Michaela ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
Magnesium and its alloys are interesting materials due to their many physical properties. They have considerable potential, especially in medical applications, where they can serve as a material for the production of orthopedic and cardiovascular implants. The disadvantage of these materials is their sensitivity to corrosion. As a result, it is necessary to know the corrosive properties of magnesium and its alloys in contact with substances that occur in the human body. Hyaluronan is a polysaccharide that is naturally present in the human body and can interact with implants. This master's thesis deals with the influence of low molecular weight (80–130 kDa) and high molecular weight (1 500–1 750 kDa) hyaluronan on the corrosion properties of magnesium alloy AZ31 in the environment of two simulated physiological solutions (0,9 % NaCl and synovial fluid). Potentiodynamic polarization (PD) and electrical impedance spectroscopy (EIS) were used for electrochemical tests. Surface analysis was performed using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to reveal the chemical composition of the corrosion products and the surface morphology after corrosion.
|
|
|
Effect of complexing agents on the preparation of phosphate coatings on AZ31 magnesium alloy
Wolanský, Petr ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
The bachelor thesis deals with the characterization of the effect of complexing agents on the preparation of phosphate (CaP) coatings deposited on AZ31 magnesium alloy. The theoretical part presents the basic characterization of magnesium alloys with emphasis on AZ31 and their corrosion properties. Furthermore, attention is paid to CaP coatings, their preparation with a focus on the chosen hydrothermal synthesis and the influence of complexing agents on the preparation of CaP coatings. In the experimental part the preparation of CaP coatings on AZ31 alloy with Mg(OH)2 interlayer is presented. Surface analysis of CaP coatings was performed using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). Chemical analysis of CaP coatings was performed using Fourier transform infrared spectroscopy. To assess the corrosion resistance of the coatings, potentiodynamic tests were performed in 0.15M NaCl. For all the selected reagents, the best corrosion properties were obtained at the lowest concentrations, while the lowest value of icorr was observed for the sample with 0.0175M EDTA, this value corresponded to the icorr of the pretreated Mg(OH)2 sample. The preparation of CaP coatings resulted in better corrosion properties than that of pure AZ31 alloy. In all samples, the presence of hydroxyapatite (HA) as the main phase in the coating was identified. From the results obtained, it can be clearly determined that the presence of complexing agents and their concentrations affect the morphology of CaP coatings and can alter the corrosion resistance. It seems that the corrosion resistance was mainly due to the Mg(OH)2 interlayer rather than the prepared CaP coatings, which could provide higher biocompatibility of the materials.
|
|
| |
|
|
Mechanical and physical properties of magnesium alloys prepared by rotary swaging
Škraban, Tomáš ; Drozd, Zdeněk (advisor) ; Mathis, Kristián (referee)
in english For their positive influence on mechanical and physical properties of the material, methods of severe plastic deformation are popular for quite some time today. Rotary swaging is one of them. With its simplicity and productivity, it has the potential for industrial use. It is a radial swaging of rods or tubes, which results in decreasing of their diameter. Influence of this method is researched on extruded rods made of magnesium alloy AZ31. Experiments are made on five samples of different degree of swaging (different diameter). This allows to research gradual evolution of properties during the swaging. Results show significant positive influence on grain size (and microstructure in general) of originally extruded rod. During swaging there is an evolution of material texture and increase in strength.
|
|
|
Effect of hyaluronic acid on the corrosion of AZ31 magnesium alloy
Holubářová, Michaela ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
Magnesium and its alloys are interesting materials due to their many physical properties. They have considerable potential, especially in medical applications, where they can serve as a material for the production of orthopedic and cardiovascular implants. The disadvantage of these materials is their sensitivity to corrosion. As a result, it is necessary to know the corrosive properties of magnesium and its alloys in contact with substances that occur in the human body. Hyaluronan is a polysaccharide that is naturally present in the human body and can interact with implants. This master's thesis deals with the influence of low molecular weight (80–130 kDa) and high molecular weight (1 500–1 750 kDa) hyaluronan on the corrosion properties of magnesium alloy AZ31 in the environment of two simulated physiological solutions (0,9 % NaCl and synovial fluid). Potentiodynamic polarization (PD) and electrical impedance spectroscopy (EIS) were used for electrochemical tests. Surface analysis was performed using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to reveal the chemical composition of the corrosion products and the surface morphology after corrosion.
|
guest ::
