|
|
Structural analysis of austenitic weld joints
Procházka, Robert ; Foret, Rudolf (referee) ; Havlík, Petr (advisor)
The bachelor thesis deals with structural analysis of austenitic weld joints by using methods of material science. The theoretical part of the thesis summarizes the problematics of welding of high-alloy steels. After the general definition of welding and weldability of high-alloy steels, the thesis focuses on structural adjustments including welding defects during the welding process. Selected methods of fusion welding that were used to create these welds are mentioned in the second half of the theoretical part. The experimental part covers the structural analysis of the welds, which consists of microstructure evaluation, chemical composition analysis, and microhardness test.
|
|
|
Influencing the surface roughness of materials created by the SLM technique and the influence of roughness on macroscopic properties
Rotter, Marek ; Havlík, Petr (referee) ; Jan, Vít (advisor)
Theses resumes the principle of SLM method and submits the most used materials for this technology and its properties. The main issue is influencing the surface roughness of these materials, when the electro-chemical polishing in the concentrated sulfuric acid was used with five difference options. It was observed, that the roughness is caused by two factors, fused nonmelted grains of metal powder and layered structure. Polishing at 8 V, 0,5 A and after 40 min was the best results, when the smooth wave surface was achieved. The Ra parameter descended from initial 5,0 m to 3,9 m after this polishing. One of the factors, which causes the high roughness, was eliminated.
|
|
|
Immiscible alloy based on Fe-Cu system
Semerák, Petr ; Havlík, Petr (referee) ; Jan, Vít (advisor)
The aim of this work is the preparation of FeCuMn alloy in equimolar composition by melting and the analysis of the resulting microstructure. The theoretical part of the work deals with miscibility and the use of immiscible systems in practical applications. Furthermore, the influence of cooling rate and the effect of the ratio of the components of the immiscible Fe-Cu system on the resulting microstructure are described. The practical part of the work presents the microstructure of FeCuMn alloy, which was prepared by melting in an induction furnace under a protective atmosphere of argon. Furthermore, the practical part deals with the chemical composition of the individual phases and the shape of the resulting phases. For the FeCuMn alloy, the melting temperature of the phases is analysed, the material is also deformed, and the hardness of the deformed and undeformed material is evaluated. In the subsequent discussion, the results from the experimental part are related to published experimental results by other authors.
|
|
|
Structural stability heterogeneous weldment of carbon/austenitic steels
Havlík, Petr ; Stránský, Karel (referee) ; Foret, Rudolf (advisor)
Heterogeneous welded joints – type ferrite/austenite is inseparable part of structure for energy industry. Welding conditions and post weld heat treatment have a significant impact on the structural stability of welded joint. The structure determines resulting mechanical properties that determine lifetime of these joints. At the same time in microstructure changes in heat affected zone of the base material is diffusion of carbon through the weld interface. This work is focused on the analysis of structural stability of heterogeneous weld carbon/austenitic steel, which was formed carbon steel 22K (base material) and austenitic buttering layer EA 395/9 with a higher content of nickel. Evaluation of the structure was focused on the structure of weld metal (Böhler FOX SAS 2) and structure of the heat affected zone of base material. Metallographic evaluation was performed on the light microscope and scanning electron microscope equipped with the energy and wave dispersive analysis, which identified the contents of substitutional elements and carbon on the interface of carbon/austenitic steel. The results of metallographic analysis were compared with measurements of Vickers hardness and microhardness and calculations using Thermo-Calc software and software SVARY. The description and evaluation of the stability of the weld joints was determined by carbon content of the course interface using wave dispersive spectroscopy. The results of energy dispersive analysis were used to determine the type of carbides present at the interface of carbon/austenitic steel.
|
|
|
Influence of thermal processing to microstructure of various steels
Kocman, Lukáš ; Havlík, Petr (referee) ; Štěpánek, Roman (advisor)
This bachelor thesis deals with the heat treatment of steel, especially measuring the influence of individual heat treatment technologies on changes in the microstructure of steels. The theoretical part of the work presents alloys of iron and carbon, furthermore describes their phase transformations in the solid state, particularly the transformation diagrams of steels. In another part of theoretical part, the basic heat treatment technologies and their influence on the mechanical properties and microstructure of steels are described. The experimental part deals with the preparation of metallographic samples and presents results of examining the microstructure and measuring the hardness of individual samples. At the end of the work the synthesis of the theoretical part and results of the experimental part is used for the partial and overall evaluation of the influence of heat treatment on the microstructure of steels.
|
|
| |
|
|
Macro and microstructure of weld joints made of titanium alloy TiAl6V4 by electron beam
Prachař, Václav ; Havlík, Petr (referee) ; Foret, Rudolf (advisor)
The aim of this bachelor thesis is to evaluate macro and microstructures of weld joints made of titanium alloy Ti6Al4V by electron beam welding with different processing parameters of electron beam and evaluate the impact of this processing parameters to the structure of resultant weld joints. The theoretical part deals with titanium and its alloys, the titanium alloy Ti6Al4V and electron beam welding technology. In the experimental part, 11 weld joints are evaluated, their macro and microstructures and hardness profiles.
|
|
|
Determination of binary phase diagram
Dobeš, Pavel ; Havlík, Petr (referee) ; Jan, Vít (advisor)
This bachelor's thesis deals with the analysis and verification of binary diagram of the Ag-Sb system. The theoretical segment of the thesis describes the sub-elements of this system, the function of binary diagrams and the methods of thermal analysis. The experimental segment mainly deals with the interpretation of DSC signal, the analysis of the microstructures of specific Ag-Sb system samples and the comparison of the acquired data with the given binary diagram.
|
|
|
Analysis of welded joints after fatigue tests
Kučera, Ondřej ; Doubrava, Marek (referee) ; Havlík, Petr (advisor)
This bachelor thesis deals with analysis of welded joints after fatigue tests . The first part of this thesis, literary research, discusses weldability of carbon steels and low-alloy steels and effect of chemical composition on weldability of materials. Further there are zones of welded joints, their microstructure and mechanisms applied described in this thesis. There are defects occurring in welded joints and their common causes and remedies described in the part of literary research dealing with defects. And the final part of the literary research deals with material fatigue, fatigue of welded joints and effect of defects, fusion zone and heat-affected zone on the fatigue of welded joints. In the experimetal part of bachelor thesis there is described experimental material, results obtain process and discussion of results.
|
|
|
The analysis of Fe-Cr-Ti binary alloys
Lauš, Lukáš ; Havlík, Petr (referee) ; Jan, Vít (advisor)
The aim of this bachelor thesis is the preparation of high volume ratio of intermediate phases in the microstructure of Ti-Fe, Fe-Cr, Ti-Cr. The bibliographic introduction includes basic information about phase equilibrium diagrams. It also includes phases in metal systems and the binary diagrams of the prepared alloys. The experimental part deals with the analysis of the alloy phases. The experimental part also deals with determination of alloys microstructure parts using calculated pseudobinary diagrams. It has been found, that although prepared from pure stock materials, the produced alloys were not binary and contained 0,6–1,4 at. % Si. Intermediate phases were found in Ti-Fe and Ti-Cr alloys. According to the calculated diagrams comparison, all of the prepared alloys were not in equilibrium.
|
guest ::
RSS feed.