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Biodegradable Mg-based materials for stents and bone implants
Zemková, Mária ; Král, Robert (advisor) ; Stráská, Jitka (referee)
The bachelor thesis is focused on the effect of mechanical processing rotary swaging (RS), specifically on the microstructure, mechanical properties and corrosion properties. The investigation was performed on the magnesium alloy AE42 with a different number of RS passes, which can be useful for medical applications. RS is more efficient and cheaper alternative to different material processing methods producing fine-grained struc- ture. Fine-grain structure with grain boundaries with high angle misorientation was achieved by this process. Microstructure was inhomogeneous - the grain size decreased from the surface to the center. An improvement of mechanical properties with the increase in the number of swaging steps was observed. Processing also led to a decrease in corrosion resistance in this alloy. Microstructure development was investigated by electron microscopy scanning. Development of mechanical properties was characterized by compression deformation tests and microhardness measurements. Linear pola- rization method was used for the interpretation of corrosion resistance. 1
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Study of properties of Titanium prepared by SPD methods
Zháňal, Pavel ; Harcuba, Petr (advisor) ; Král, Robert (referee)
In present work the properties of comercially pure titanium fouth grade processed by equal channel angular pressing (ECAP) were studied. Experimental techniques such as Vickers microhardness, measurement of electrical resistivity, light and electron microscopy were used in this research. The dependence of the degree of the strain imposed by ECAP on microhardness of the material was measured. Microhardness measurement was used to indirectly investigate thermal stability of the prepared material, which is essential for ultra fine grained (UFG) materials. That was also the reason for establishing dependence of the electrical resistivity on the temperature. This method allows to detect changes in the material microstructure. Using scanning electron microscopy (SEM) the results obtained by previous methods were confirmed. It was found that the UFG titanium processed by ECAP is thermally stable aproximatelly up to 450řC. At this temperature begins recovery of the material which results in a decrease of the microhardness values and electrical resitivity. For the temperatures higher than 520řC material recrystalization begins.
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Effect of microstructure on mechanisms of plastic deformation in fine-grained magnesium alloys
Minárik, Peter ; Král, Robert (advisor) ; Hadzima, Branislav (referee)
In this work were studied effects of the grain refinement on the mechanical properties and the corrosion resistance of magnesium alloys potential for medical applications - AE21 and AE42. Mechanical properties changed after ECAP pressing in consistency with literature data. Enhanced corrosion resistance in AE42 alloy was achieved by the grain refinement. Corrosion layer created on the surface was observed by light and electron microscopy. Effect of the grain size on the character of the corrosion layer was investigated. AE42 alloy is suitable for further investigation as potential biodegradable material. AE21 alloy was excluded from further investigation due to low corrosion resistance even after ECAP treatment.
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