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Corrosion Resistance of Structural Magnesium Alloys
Tkacz, Jakub ; Pacal, Bohumil (referee) ; Hadzima, Branislav (referee) ; Havlica, Jaromír (advisor)
This thesis describes magnesium alloys, their properties and methods of their production. However, experimental part is focused on AZ91 magnesium alloy. Conversion coatings were prepared on the AZ91 surface – chromate coating, phosphate permanganate coating and fluoride coating. Corrosion resistance of the prepared coatings were compared by immersion tests and by potentiodynamic methods. Evaluation of corrosion resistance by immersion tests was successful only for phosphate permanganate coating. Only this coating was removed during cleaning of the samples. For comparison of corrosion resistance was important to find the correct procedures and optimize the measurements methods. For these purposes have been chosen galvanic zinc coating on steel sheets. Thickness of the zinc coating were 8 and 30 microns. This coatings provide uniform zinc surface without heterogenities which was important for the potentiodynamic measurements. After optimization methods for potentiodynamic measurements by galvanic zinc coatings have been measured magnesium alloy AZ91 uncoated and coated by conversion coatings. For uncoated AZ91 magnesium alloy was determined suitable method so called virgin cathodic curve. On the other hand, for the coated AZ91 magnesium alloys was determined suitable method so called combined curve, within which we measured cyclic voltammetry curve (± 5 mV) and then virgin anodic curve.
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Galvanic plating of magnesium alloy with Ni-P bond coat
Zahálka, Martin ; Kosár, Petr (referee) ; Wasserbauer, Jaromír (advisor)
Cílem této diplomové práce jse najít nejnižší možnou tloušťku nikl-fosforového povlaku, který může být galvanicky pokoven mědí bez defektů na horčíkové slitině, nikl-fosforového nebo měděného povlaku. V teoretické části jsou shrnuty poznatky o hořčíkových slitinách a jejich korozi. Navíc se teoreticá část zaměřuje na popis procesu bezproudého niklování a elektrochemického pokovování mědí a jejich porovnání. Na konci teoretické části je shrnut současný výzkum o elektrochemickém pokovování hořčíkových slitin. V experimentální části byl popsán proces přípravy povlaků Ni-P a Cu na horčíkové slitině AZ91. Na jedné vrstvě a dvojité vrstvě Ni-P povlaku byla provedena elektrodepozice mědi. Navíc byl diskutován vliv předůpravy před samotnou elektrodepozicí mědi. Za účelem zjištění korozních vlastností vzorků byl vykonán potenciodynamický test. Následně byly připraveny metalografické výbrusy jednotlivých vzorků a pomocí světelného a rastrovacího elektronového mikroskopu byla provedena charakterizace. Na konec bylo zjištěno prvkové složení jednotlivých povlaků pomocí EDX analýzy.
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Magnesium alloys
Březina, Matěj ; Šoukal, František (referee) ; Zmrzlý, Martin (advisor)
The study is focused on corrosion and corrosion protection of magnesium and magnesium alloys. The theoretical part describes properties of magnesium and magnesium alloys. It shows their advantages as well as their disadvantages and discusses ideal use for these alloys. The theoretical part analyses basic corrosion characteristics and typical corrosion processes. It deals with types of corrosion protection and ways of its use. The experimental part was focused on metallographic analysis and corrosion behavior of magnesium alloy AZ91. Metallographic methods were used for preparing AZ91 to corrosion tests. The experimental part compared corrosion rate and degradation of pure AZ91 and AZ91 with conversion coating (phosphate-permanganate) in 3,5% sodium chloride solution in times: 1, 8 and 48 hours.
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Fatigue endurance of extruded Mg alloy AZ91E
Sobola, Petr ; Štěpánek, Roman (referee) ; Pantělejev, Libor (advisor)
This thesis deals with fatigue behaviour of magnesium alloy AZ91E produced by extrusion. In the frame of this work, basic mechanical characteristics and data from performed fatigue tests were obtained. Further metallographic analysis of microstructure and fractographic analysis of broken specimens after fatigue tests were carried out.
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Mg-alloy die-castings for automotive industry
Hejduk, Oldřich ; Pacal, Bohumil (referee) ; Čech, Jaroslav (advisor)
The thesis dealt in the degree of the bachelor study covers Mg-alloy die-castings for automotive industry. Major destination is description properties of Mg-alloy, special properties of Mg-alloy die-castings. Experimental part of this thesis deals posibility of mensuration and calculation residual tightness on the Mg-alloy die-casting AZ91D.
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Application of magnesium alloys castings
Pernica, Vítězslav ; Liškutín, Petr (referee) ; Roučka, Jaromír (advisor)
Magnesium alloys are still idle in technical applications because of their properties. The history of metal is not very old, the first application of its alloy started on the beginning of the 20th century. Magnesium is very light. Its weight is about one third less than the weight of aluminum and it is the third most frequented structural metal. However its preparation and processing can be problematical because magnesium has high affinity to oxygen. It causes intensive burning. During the century of stature have been improved both production and alloys. The usage of magnesium alloys took more importance and it is the most used alloy in automotive field sofar. Recently its demand expands mainly in electrotechnics. Next usage we can find in aeronautics, energetics, military and many other branches.
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Characterization of the thermally-sprayed metal-ceramic WC-CoCr coating on the AZ91 magnesium alloy
Knoflíčková, Lenka ; Wasserbauer, Jaromír (referee) ; Buchtík, Martin (advisor)
The aim of this bachelor thesis is to evaluate metal-ceramic coating WC-CoCr on magnesium alloy AZ91 to terms of microstructure, chemical and phase structure and mechanical properties. Deposition was made by HVOF (High Velocity Oxy-Fuel). The theoretical part is devoted to magnesium alloys focusing on alloy AZ91. Further there is said about methods of heat spraying. Where this part is focused on metal-ceramic WC-CoCr coatings made by HVOF method. The theoretical part is ended by current research, that is focused on characterization of WC-CoCr on magnesium alloys. Experimental part is about characterization of microstructure of alloy AZ91, WC-CoCr powder and WC-CoCr coating on magnesium alloy AZ91 with optical, SEM and XRD analysis. With heat spraying was observed that phase W2C was made by decay of phase WC in coating which leaded to dissolve of WC in matrix. For measuring of mechanical properties was used measurement by Vickers (hardness test). As result of WC-CoCr coating on surface of magnesium alloy AZ91 was increase of average hardness from 71 ± 5 HV0,3 to 1116 ± 109 HV0,3.
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Characterization of the thermally-sprayed metal-ceramic WC-CoCr coating on the AZ91 magnesium alloy
Knoflíčková, Lenka ; Wasserbauer, Jaromír (referee) ; Buchtík, Martin (advisor)
The aim of this bachelor thesis is to evaluate metal-ceramic coating WC-CoCr on magnesium alloy AZ91 to terms of microstructure, chemical and phase structure and mechanical properties. Deposition was made by HVOF (High Velocity Oxy-Fuel). The theoretical part is devoted to magnesium alloys focusing on alloy AZ91. Further there is said about methods of heat spraying. Where this part is focused on metal-ceramic WC-CoCr coatings made by HVOF method. The theoretical part is ended by current research, that is focused on characterization of WC-CoCr on magnesium alloys. Experimental part is about characterization of microstructure of alloy AZ91, WC-CoCr powder and WC-CoCr coating on magnesium alloy AZ91 with optical, SEM and XRD analysis. With heat spraying was observed that phase W2C was made by decay of phase WC in coating which leaded to dissolve of WC in matrix. For measuring of mechanical properties was used measurement by Vickers (hardness test). As result of WC-CoCr coating on surface of magnesium alloy AZ91 was increase of average hardness from 71 ± 5 HV0,3 to 1116 ± 109 HV0,3.
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Influence of surfactants in electroless nickel bath on properties of Ni-P coatings on AZ91 magnesium alloy
Buday, Patrik ; Wasserbauer, Jaromír (referee) ; Buchtík, Martin (advisor)
This bachelor thesis deals with the effect of surfactants on mechanical properties and structure of Ni-P coatings on AZ91 magnesium alloy. The theoretical part of the thesis includes summary of basic knowledge about magnesium alloys, surfactants and electroless deposition of Ni-P coatings, including a detailed description of Ni-P reduction on substrate. The theoretical part is concluded by current research in the field of Ni-P coatings. In the experimental part, morphology of Ni-P coatings was observed by electron microscopy (SEM). Using a light microscope (LM), the effect of surfactants on the deposition rate was observed. By means of energy dispersion analysis, the average phosphorus content of Ni-P coatings was determined. The hardness as a mechanical property of these coatings was determined using a micro hardener.
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