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Preparation and characterization of Ni-P coating on AZ91 cast magnesium alloy
Brescher, Roman ; Buchtík, Martin (referee) ; Wasserbauer, Jaromír (advisor)
This bachelor thesis deals with electroless deposition of nickel-phosphoric (Ni-P) coating on AZ91 magnesium alloy. At the beginning of the theoretical part, there is a summary of basic knowledge about magnesium alloys with focus on AZ91 alloy and the influence of alloying elements and impurities and its microstructure. The theoretical part continues with the discussion of the Ni-P coating, focusing on the composition of the bath, the influence and the effect of its individual components. Next, there is a comparison with galvanic nickeling. At the end of the theoretical part, the current research of the use of electroless deposition of Ni-P layer on AZ91 magnesium alloy is summarized. In the practical part, there is the preparation of the Ni-P coating on the AZ91 magnesium alloy, the observation the microstructure of the magnesium alloy and the Ni-P layer, and rate of deposition, the thickness, the microhardness and the composition of the coating was measured. The effect of its heat treatment was also observed. It has been found that it is possible to produce a high-quality Ni-P coating on an AZ91 magnesium alloy which has no visible defects or obvious undesirable interlayers, however the heat treatment of the coating causes its cracking. To determine the corrosion resistance, a potentiodynamic measurement was performed, resulting in the finding that the Ni-P coating without heat treatment was a suitable corrosion protection. However, after heat treatment, the corrosion resistance due to cracking of the surface deteriorated to a level of bare AZ91 alloy.
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Fluoride coatings on magnesium prepared in melts
Drábiková, Juliána ; Richtera, Lukáš (referee) ; Zmrzlý, Martin (advisor)
This work deals with the corrosion protection of magnesium alloy AZ31, AZ61, AZ91 using fluoride conversion coating prepared from Na[BF4] melt. The theoretical part describes the properties of magnesium alloys, the recent results of fluoride conversion coatings preparation and analysis of the available literature about the properties of salt Na[BF4] and its decomposition products. The experimental part was devided into two main sections. The first deals with the corrosion resistance of the treated magnesium alloys (AZ31, AZ61, AZ91 and AZ91 annealed) in the Na[BF4] melt. Corrosion resistance was tested using potentiodynamic tests and tests in the corrosion chamber. In the second part, the mechanism has been studied for preparing fluoride conversion coating, where it was shown that in air-free atmosphere the oxidizing agent in the process is boron, which is reduced from BIII to B0, and thereby enables the fluoride conversion coating.
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Processing of magnesium alloys using selective laser melting
Kaščák, Pavol ; Paloušek, David (referee) ; Suchý, Jan (advisor)
The processing of magnesium-based materials with Selective laser melting technology is due to its high reactivity in the initial stages of development. This bachelor thesis deals with the elucidation of impacts of individual process parameters in processing of magnesium alloys on the resulting material porosity. The aim is to develop initial experiments for the shift in the processing of magnesium alloys by additive technologies. The theoretical part contains an insight into the SLM technology and an overview of the current state of knowledge of processing of magnesium alloys by this technology. By the analysis of the theoretical part, the main volume test of this thesis has been designed. The selected material for this test was the biodegradable magnesium alloy WE43. According to the author's knowledge, no research has been published on this alloy so far. Based on the results of the experiment, the dependencies of the individual process parameters were made on the resulting relative density of the samples. At the end, the outputs were compared with the literature.
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Electrochemical characteristics of AZ31 and AZ61 magnesium alloys in Hanks‘ solutions
Minda, Jozef ; Wasserbauer, Jaromír (referee) ; Tkacz, Jakub (advisor)
This thesis deals with the characterization of electrochemical corrosion properties of magnesium alloys as promising materials for biomedical applications. The wrought alloys AZ31 and AZ61 were used and exposed to corrosive environments of Hanks solutions (SBF) to simulate environmental conditions in living organisms. For the evaluation of the surfaces was used scanning electron microscopy (SEM) with elemental analysis measured by energy-dispersive spectroscopy (EDS). Short-term (5 min) and long-term (72 h) corrosion tests were conducted in order to optimize the measurement methodology and obtain corrosion parameters - especially corrosion potential (Ekor), corrosion current density (ikor) and polarisation resistance (RP). To evaluation of the short-term tests were by potentiodynamic tests, namely the linear polarization (LP) test. Long-term tests were measured by electrochemical impedance spectroscopy (EIS). Effects of the composition of the alloys (AZ31 and AZ61), surface treatment (grinding and polishing) and the composition of the solution (SBF without Ca, Mg, and with Ca, Mg) were compared. Complex corrosion behaviour in time was characterized and corrosion mechanisms were discussed.
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Processing of magnesium alloys using selective laser melting
Kaščák, Pavol ; Paloušek, David (referee) ; Suchý, Jan (advisor)
The processing of magnesium-based materials with Selective laser melting technology is due to its high reactivity in the initial stages of development. This bachelor thesis deals with the elucidation of impacts of individual process parameters in processing of magnesium alloys on the resulting material porosity. The aim is to develop initial experiments for the shift in the processing of magnesium alloys by additive technologies. The theoretical part contains an insight into the SLM technology and an overview of the current state of knowledge of processing of magnesium alloys by this technology. By the analysis of the theoretical part, the main volume test of this thesis has been designed. The selected material for this test was the biodegradable magnesium alloy WE43. According to the author's knowledge, no research has been published on this alloy so far. Based on the results of the experiment, the dependencies of the individual process parameters were made on the resulting relative density of the samples. At the end, the outputs were compared with the literature.
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Preparation and characterization of Ni-P coating on AZ91 cast magnesium alloy
Brescher, Roman ; Buchtík, Martin (referee) ; Wasserbauer, Jaromír (advisor)
This bachelor thesis deals with electroless deposition of nickel-phosphoric (Ni-P) coating on AZ91 magnesium alloy. At the beginning of the theoretical part, there is a summary of basic knowledge about magnesium alloys with focus on AZ91 alloy and the influence of alloying elements and impurities and its microstructure. The theoretical part continues with the discussion of the Ni-P coating, focusing on the composition of the bath, the influence and the effect of its individual components. Next, there is a comparison with galvanic nickeling. At the end of the theoretical part, the current research of the use of electroless deposition of Ni-P layer on AZ91 magnesium alloy is summarized. In the practical part, there is the preparation of the Ni-P coating on the AZ91 magnesium alloy, the observation the microstructure of the magnesium alloy and the Ni-P layer, and rate of deposition, the thickness, the microhardness and the composition of the coating was measured. The effect of its heat treatment was also observed. It has been found that it is possible to produce a high-quality Ni-P coating on an AZ91 magnesium alloy which has no visible defects or obvious undesirable interlayers, however the heat treatment of the coating causes its cracking. To determine the corrosion resistance, a potentiodynamic measurement was performed, resulting in the finding that the Ni-P coating without heat treatment was a suitable corrosion protection. However, after heat treatment, the corrosion resistance due to cracking of the surface deteriorated to a level of bare AZ91 alloy.
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Study of deformation mechanisms in extruded magnesium alloys containing neodymium and yttrium
Hojnoš, Peter ; Minárik, Peter (advisor) ; Chmelík, František (referee)
Submitted work shows results of the investigation of ternary (WN43) and two binary magnesium alloys containing neodymium (2Nd) and yttrium (4Y) extruded at two different extrusion rates (2 and 5 mm/s). Microstructure of the investigated samples was analysed by light microscope. Additionally, texture of all samples was measured by X-ray diffraction. Mechanical properties were studied by compression deformation tests with two different deformation directions with respect to the processing direction. Acoustic emission was recorded during the deformation tests in order to correlate deformation behaviour with the micros- tructure. Analysis of the acoustic emission helps to identify deformation micro- mechanisms acting during the mechanical straining. Additionally, effect of sample size and deformation rate on the deformation mechanisms was investigated. 1
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Electrochemical characteristics of AZ31 and AZ61 magnesium alloys in Hanks‘ solutions
Minda, Jozef ; Wasserbauer, Jaromír (referee) ; Tkacz, Jakub (advisor)
This thesis deals with the characterization of electrochemical corrosion properties of magnesium alloys as promising materials for biomedical applications. The wrought alloys AZ31 and AZ61 were used and exposed to corrosive environments of Hanks solutions (SBF) to simulate environmental conditions in living organisms. For the evaluation of the surfaces was used scanning electron microscopy (SEM) with elemental analysis measured by energy-dispersive spectroscopy (EDS). Short-term (5 min) and long-term (72 h) corrosion tests were conducted in order to optimize the measurement methodology and obtain corrosion parameters - especially corrosion potential (Ekor), corrosion current density (ikor) and polarisation resistance (RP). To evaluation of the short-term tests were by potentiodynamic tests, namely the linear polarization (LP) test. Long-term tests were measured by electrochemical impedance spectroscopy (EIS). Effects of the composition of the alloys (AZ31 and AZ61), surface treatment (grinding and polishing) and the composition of the solution (SBF without Ca, Mg, and with Ca, Mg) were compared. Complex corrosion behaviour in time was characterized and corrosion mechanisms were discussed.
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Fluoride coatings on magnesium prepared in melts
Drábiková, Juliána ; Richtera, Lukáš (referee) ; Zmrzlý, Martin (advisor)
This work deals with the corrosion protection of magnesium alloy AZ31, AZ61, AZ91 using fluoride conversion coating prepared from Na[BF4] melt. The theoretical part describes the properties of magnesium alloys, the recent results of fluoride conversion coatings preparation and analysis of the available literature about the properties of salt Na[BF4] and its decomposition products. The experimental part was devided into two main sections. The first deals with the corrosion resistance of the treated magnesium alloys (AZ31, AZ61, AZ91 and AZ91 annealed) in the Na[BF4] melt. Corrosion resistance was tested using potentiodynamic tests and tests in the corrosion chamber. In the second part, the mechanism has been studied for preparing fluoride conversion coating, where it was shown that in air-free atmosphere the oxidizing agent in the process is boron, which is reduced from BIII to B0, and thereby enables the fluoride conversion coating.
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