Solid State Phenomena Vol. 176

Abstract: Today the aluminium refining process, especially barbotage is one of the most essential necessary technological stages in obtaining aluminium. It gives possibility to remove undesirable hydrogen and non-metallic and metallic inclusions from aluminium. Phenomena that take place during the barbotage process are rather complicated, but the knowledge about their character enables to optimize and control this process. Modelling research is used to outline these phenomena. Physical and mathematical modelling can be applied in carrying out aluminium barbotage process. Mathematical modelling uses numerical methods to solve the system of differential equations. The paper presents results of physical and numerical modelling of the refining process taking place in the continuous reactor URC-7000. Physical modelling was carried out for the different flow rate of refining gas (argon). It was in the range between 2 to 25 dm3/min. Numerical calculation was done using commercial program in Computational Fluid Dynamics (CFD). Model Volume of Fluid (VOF) was applied in modelling the multiphase flow. Obtained results were compared in order to verify the numerical settings and correctness of the choice.

Abstract: Bayern`s method is the first stage of obtaining primary aluminium. The product of this process is alumina. The paper presents how much alumina was produced in the last couple of years and who were its leading producers. As the main ore for alumina production is bauxite; it was necessary to describe its characteristics: chemical composition and types of bauxites. Short description of the method (digestion, precipitation and calcination) was presented. During this process a lot of pollution is usually emitted to the atmosphere, but mostly a lot of red mud is generated. This is the main waste of the process, which at the same time is very harmful to the environment. The ways red mud is disposed or utilized were reviewed. Two kinds of red mud disposal are known: wet and dry disposal. Both were characterized and their advantages and disadvantages were outlined. The possibilities of red mud utilization were shown. The focus was put on iron recovery or recovery of compounds such as Al2O3 or TiO2. The use of red mud in building materials was discussed. Radioactivity of such materials was also analyzed. Possibility of red mud utilization as a pigment and radiopaque material was also mentioned.

Abstract: . In this study, commercial Al was subjected to plastic deformation by multi-axial compression. The microstructure and mechanical properties in dependence on effective strain were studied. Aluminum was processed to effective strain f = 9.6. The misorientation distribution and subgrain/grain size were analyzed by using a scanning electron microscopy (SEM) equipment with electron back scattered diffraction (EBSD) facility. The dislocation microstructure was investigated by a scanning transmission electron microscope (STEM). The mechanical properties as: yield strength (YS), ultimate tensile strength (UTS), uniform and total elongation were performed on MTS QTest/10 machine equipped with digital image correlation method (DIC). Deformation of Al by the multi-axial compression leads to grain refinement to ultra-fine grains (UFGs) and improvement in strength properties. Material exhibits the following strength parameters: UTS: 129 MPa, YS: 124 MPa after deformation at f = 9.6. These values are about two times higher compared with initial state.

Abstract: The effect of overheating on the solidification process and microstructure evolution in AlSi17 silumin was discussed. The alloy melt was held for 40 minutes at 780, 860, 940 and 1020oC, and then cast at a temperature of 780oC to standard ceramic probe. Characteristic parameters of the AlSi17 alloy solidification process, especially Tliq, TE, Tsol, were determined. Examinations of microstructure were also carried out, showing that the higher was the overheating temperature, the higher was the degree of the primary silicon crystals refinement.

Abstract: The article presents the course and the results of research on material and technological welding conditions of different aluminium alloys using low energy welding methods (CMT and ColdArc) as well as discusses the properties of welded joints and the application fields of modern low energy welding devices for joining thin aluminium sheets.

Abstract: The mechanical properties of composite materials with glassy carbon (GC) have been presented. The effect of size and reinforcement value on tensile strength, impact and tribological characteristics (coefficient of friction and wear) were estimated. It has been found that the reinforcement value decide on mechanical properties. Enlargement of particles value leads to decreasing of tensile strength and impact strength. It has been shown that particle size has small influence on studied properties. Destruction energy for the composites with particles exceeding 100 µm is similar. The measurement of coefficient of friction proved, that increase of reinforcement value leads to decreasing of coefficient of friction from 0.4 for 5% value to about 0.12 for 20% of particle value. The coefficient of friction is comparable for the composites containing particles of 200 µm size and is less dependent on reinforcement value. However size of the particles decide on the character of coefficient of friction changes.

Abstract: The article presents the results of the first phase of research on the development of manufacturing composites by pilot-scale technology. Producing of composite suspension in sufficient quantity to obtain approximately 50 casting pistons in one production cycle was the aim of this study. This allowed to assess the stability of the composite suspension manufacturing process and above all stability the casting process. Composite suspension (AlSi7Mg/SiCp and heterophase SiCp+Cg ) were prepared in one technological cycle including refining and modification of the alloy matrix, the introduction of ceramic particles and the homogenization of the suspension under reduced pressure. Objective of this study was to determine the basic parameters of the suspension of the manufacturing process, such as metal refining period, the rate of particles introduction and time of homogenization. In addition, as a evaluation criterion of quality the manufactured composite material accepted the possibility of pre-cast piston machining.

Abstract: Interaction of Al-Si alloys with SiC/C ceramic particles and their influence on microstructure of composites was discussed. This article presents a significant effect of modifying additives introduced into liquid aluminium. As it was shown in the research, Mg and Sr modifiers improve wetting conditions in Al/SiCp+Cp systems, as well as influence the composite’s structure and the structure of the interface between the components. The microstructure observations were performed using light microscopy (OLYMPUS GX 71) and scanning electron microscopy (PHILIPS XL30). Moreover, local analyses of chemical compositions as well as chemical elements mapping were performed using an EDX module for microarea chemical analysis. Based on structural studies, it was found that chemical composition of the aluminium alloy and its modification are equally important parameters.

Abstract: It is required of sand casting magnesium used for aircraft industry to be, among others, increasingly creep-resisting. This paper describes microstructure and properties of chosen magnesium sand casting alloys, intended for usage at ambient and elevated temperature. The first part describes the most popular magnesium alloy Mg-9Al-1Zn (AZ91), which, due to the presence of Mg17Al12 phase in its structure, can be used only up to the temperature of ~120°C. The second part describes Mg-5Y-4RE-Zr (WE54) alloy, which can be used at the temperature of up to ~250°C. Unfortunately, its usage is very limited due to high price. The third part characterizes Mg-3Nd-1Gd-Zr (EV31A) alloy, which has properties similar to Mg-5Y-4RE-Zr alloy, but lower price. This paper also discusses the potential applications of these alloys.