Solid State Phenomena Vol. 226

Abstract: The paper characterized the phase composition, microstructure and selected mechanical properties at room temperature and at temperature corresponding to the expected operating conditions of two-phase Ti-47Al-2W-0.5Si cast alloy melted in a vacuum induction furnace in a special graphite crucibles.

Abstract: Welding fume emitted while welding stainless chromium-nickel steels contains mainly nickel oxides (NiO, NiO₂ and Ni₂O₃). Welding in the inert gas shielding as well as plasma and laser cutting of parent materials of a high content of nickel ranks among the welding processes characterised by the highest concentrations of nickel oxides in welding fume. The predicted content of this element in the mass % range of 0.7 to 6% has been adopted as a criterion for the selection of the analytical method of the determining nickel content in the welding fume. Determination of nickel is based on dissolution of the sample in a mixture of acids, separation of nickel in the form of solid dimethylglyoxime nickel (II) and gravimetric determination. The adopted method of nickel determination in the welding fume proved to be an effective and inexpensive solution.

Abstract: Based on the electrical parameters of a 20 MVA ferrosilicon furnace, a methodology of identification of characteristic ferrosilicon smelting states described as carbon excess and carbon deficiency in the reaction zones ('over-coked', 'under-coked') has been presented. Relations between the electrical parameters and assessments made by furnace operators regarding characteristic furnace states related to amounts of carbon in the reaction zones have been demonstrated. The results show that the reactive power measurements as well as the k, c₃ (Andreae’s, Westly’s) parameters, provide the same information on the furnace state and have a close relation with resistivity of the current-conducting zones. Similar information on the level of carbon balance in the reaction zones is obtained from the harmonic analysis of phase voltages and currents or measurements of higher harmonic components using high-pass filters.

Abstract: The goal of this study was to investigate the origin of ferroelectricity in Bi₄Ti₃O₁₂. The bismuth titanate Bi₄Ti₃O₁₂ (BTO), which belongs to the Aurivillius family, is one of the most interesting compounds among the bismuth-based layered ceramics. BTO is a ferroelectric material with wide applications in the electronic industry, as capacitors, transducers, memory devices and sensors. Aurivillius structures are described with a general formula following form:A_m-1Bi₂B_mO_3m-1. BTO ceramic materials is an Aurivillius structure with m = 3. This ceramic materials were prepared by conventional mixed-oxide method of the solid state reaction. The temperature of the Bi₄Ti₃O₁₂ sintering was selected on basis of thermogravimetric studies. The crystal structure of Bi₄Ti₃O₁₂ was examined at room temperature with an X-ray diffraction method. Phase formation behavior was investigated using the differential thermal analysis (DTA) and the thermal gravimetric (TG). The microstructure was investigated by SEM method. Based on the Dorrian’s model, the value of displacements between bismuth ions and oxygen octahedra was calculated.

Abstract: In the paper, the effect of long-term annealing (to 500 h) on the microstructure and hardness of two-phase titanium alloy which represent group of α+β (Ti-6Al-4V) with 0.7 wt. % carbon content was present. The stability of microstructure after long-term annealing was conducted to alloys in hardening state (after solution treatment and aging). Annealing was carried out at a temperature above the operating temperature of commercial titanium alloys without carbon content. The analysis of changes in the microstructure at research range of annealing time indicates its stability, which was confirmed by hardness test of investigated alloys. For comparison to Ti-6Al-4V-0.7C alloy, the microstructure stability research at 420oC was conducted for classical alloy contain no carbon. This alloy was previously subject solution and aging treatment under the same conditions as tested alloy.

Abstract: The main purpose of this paper was biomechanical analysis of hip joint endoprosthesis – femur systems by means of the Finite Element Method. During the analysis two endoprostheses with differential geometric features were selected. Geometric models of analysed implants were compiled on the grounds of real models like Merotan and The DePuy Proxima which were chosen from series diamensional. Afterwards the models were discretization and boundary conditions were set. Those boundary conditions with right accuracy copied a phenomena which occurred in real models - the Pauwels model. The field of analysis involved determination of the state of displacements, strains and stresses which were cut down in the of endoprosthesis – bone systems. The analysis that was carried out constitute the basics for optimisation of implant geometry and right selection of material’s mechanical properties to its production.

Abstract: In the paper, the new highly alloyed Cr-V-Mo stainless tool steel produced via the powder metallurgy method was examined. The Elmax steel is a new-generation sintered tool steel characterised by high resistance to wear and corrosion and very good dimensional stability. The purpose of the paper was to analyse the influence of the rate of cooling from the temperature of austenitization and of an additional sub-zero treatment on the microstructure, phase composition and the curve of mechanical properties of steel during tempering. It has been found that a sub-zero treatment decreased the retained austenite fraction in the steel structure after hardening in oil or compressed air. The use of a sub-zero treatment on specimens after hardening had no significant effect on steel hardness after tempering, but it negatively affected the course of bending strength and impact strength of steel. Based on the obtained results it has been found that optimum mechanical properties for the Elmax steel were obtained after hardening from a temperature of 1080°C in compressed air (without a sub-zero treatment) and tempering at a temperature of 180°C.

Abstract: Aluminium alloys are characterized by a number of advantageous properties , which include: low density ,high relative strength , high electrical and thermal conductivity , ease of machining and good dumping features. Particular interesting are high-strength aluminum alloys of zinc, magnesium and copper. These alloys are used mainly in aircraft, building &structure, electrical, electrical power and automotive industry. A significant problem associated with the use of high-strength aluminium-zinc alloys is their insufficient resistance to corrosion. Improvement of corrosion resistance can be obtained by application of alloy micro-additives. The article shows results of examinations related to influence of rare earth additive on the structure and hardness of AlZn12Mg3.5Cu2.5 alloy. The scope of examination included: structure testing using scanning microscope, X – ray microanalysis, hardness test. Examinations have shown higher hardness of samples with rare earth additives. Was found , that rare earth addition influences on more fine –grained structure of the AlZn12Mg3.5Cu2.5 alloy.

Abstract: One of the most advanced manufacturing technologies is laser welding. Due to the limited power of the beam, the difficulty of precise preparation of the joint and the possibility of hardening in a narrow heat affected zone laser welding is used only for basic low carbon and low alloy steels. In this work the effects of autogenous weld parameters on microstructure and properties of the Inconel 617 alloy were studied. For this purpose the technological test of laser autogenous weld was performed.