Thesis dissertate power reactors and analyses techniques of an air-core power coils and inductors with ferromagnetic circuit and an air gap. Construction of the inductors verified the accuracy of the calculated values against the measured parameters. According to the outcome of this analysis, corrections of the design process are derived. Thesis design optimization to minimize size, weight, efficiency and in comparsion of these two factoctors.

The aim of this dissertation work is the evaluation of the influence of nickel alloying on the structure and mechanical properties, both monotonic and dynamic, of nodular cast iron with ferritic and bainitic matrix. Two chock melts with 0.5 and 2.7 % Ni were used to study the nickel influence. The quantitative evaluation of structure of these melts using image analysis was done and basic tensile mechanical properties were determined. Subsequently, the time optimization of two-stage ferritic annealing and isothermal austempered heat treatment at 375 °C was performed with the aim to obtain optimal ferritic and bainitic structures with best static and dynamic mechanical properties. After ferritic annealing the nickel alloying contributes to substitution hardening of ferritic matrix which positively affects its strength and other mechanical properties. The higher nickel content in the bainitic structure causes the shift of phase transformation times to longer times which results in restricted production of small carbides and in bigger volume of retained austenite. These features were confirmed by observation in transmission electron microscope. Precise tensile and low cycle fatigue tests at temperatures 23 and – 45 °C were performed on the optimized structures of both nodular cast irons. As a result of the notch effect of graphite nodules, microplastic deformation of both nodular cast irons was observed at stresses which were lower than the yield stress. The Hollomon's equation very well describes the individual parts of tensile curves for both nodular cast irons including their mutual comparison. From the low cycle fatigue tests, the cyclic hardening/softening curves, the evolution of elastic modulus and hysteresis loop shape parameters, cyclic stress-strain curves and fatigue life curves were obtained for both temperatures and materials. Moreover, the decrease of retained austenite volume was measured by neutron diffraction and the evolution of surface relief was characterized during cyclic straining for both austempered nodular cast irons at both temperatures. On the basis of these results both cyclic plasticity and fatigue degradation mechanisms in relation to the cyclic strain localization were described for both nodular cast irons.

<p>Structural metallic materials exposed to energetic particle bombardments often experience various types of irradiation-induced microstructural damage, thus degrading the mechanical properties of the materials in form of irradiation hardening and embrittlement. Nanostructured materials have shown better radiation resistance than their coarse-grained (CG) counterparts due to the existence of abundant defect sinks, such as grain boundaries, twin boundaries, and phase boundaries. However, recently developed nanocrystalline (NC) steels show limited room-temperature tensile ductility (< 1%), which may become a concern for their future application for nuclear reactors. The focus of this thesis is to explore the strength-ductility dilemma in modified 9Cr1Mo (T91) ferritic/martensitic (F/M) steel processed by thermomechanical treatment (TMT) and surface severe plastic deformation (SSPD) with an attempt to fabricate strong, ductile and radiation resistant F/M steels. </p> <p><b>Carbon partitioning</b> between the quenched martensite and the other phases (bainitic ferrite or retained austenite) is critical for enhancing the strength and ductility of T91 steel. The tensile properties of partially tempered (PT) T91 steel can be tailored through introducing bainitic ferrite with high-density nanoscale transition carbides and refined lath martensite. In addition, retained austenite was introduced by increasing the carbon concentration of T91 steel to 0.6 wt.%. The carbon-modified steel processed by quenching partitioning (Q-P) treatment exhibits an ultrahigh strength, ~ 2 GPa, with a uniform strain of ~ 5% due to the existence of coherent carbides, ultrafine martensite and retained austenite. </p> <p>Meanwhile, surface mechanical grinding treatment (SMGT) on T91 steel reveals that introducing <b>gradient structures</b> on the sample surface contributes to a higher strength and an improved plasticity than its homogeneously structured counterpart. The deformation mechanism of the gradient structures was investigated with the assistance of quasi <i>in situ</i> crystal orientation analyses. Furthermore, <i>ex situ</i> He ion irradiation on the gradient T91 steel indicates that radiation-induced damage, such as bubble-induced swelling and irradiation hardening, were gradually mitigated by grain refinement from the sample surface to the center, resulting in superior radiation resistance. The results obtained from this thesis may facilitate the design and fabrication of strong, ductile and radiation-tolerant F/M steels.</p>