Phase compositions of composite materials determine their performance as well as physical and mechanical properties. Depending on the type of applied matrix and the kind, amount and morphology of the matrix reinforcement, it is possible to shape the material properties so that they meet specific operational requirements. In the paper, results of investigations on silver alloy matrix composites reinforced with ceramic particles are presented. The investigations enabled evaluation of hardness, tribological and mechanical properties as well as the structure of produced materials. The matrix of composite material was an alloy of silver and aluminium, magnesium and silicon. As the reinforcing phase, 20-60 μm ceramic particles (SiC, SiO2, Al2O3 and Cs) were applied. The volume fraction of the reinforcing phase in the composites was 10%. The composites were produced using the liquid phase (casting) technology, followed by plastic work (the KOBO method). The mechanical and tribological properties were analysed for plastic work-subjected composites. The mechanical properties were assessed based on a static tensile and hardness tests. The tribological properties were investigated under dry sliding conditions. The analysis of results led to determination of effects of the composite production technology on their performance. Moreover, a relationship between the type of reinforcing phase and the mechanical and tribological properties was established.
One of the promising technology that guarantee the high-purity of the processed metal is induction skull melting. The quality of the melting process within such a system strongly depends on the cold crucible design. Hence, the experimental investigation of the cold crucible melting was performed. The experimental investigation was performed for various initial mass of the load. The results of that analysis were used for the assessment of the alloy temperature during the process, free surface shape and the area as well as the liquid metal emissivity. The collected results of the thermal analysis showed that the temperature of molten metal increased within the power input increase. Moreover, results of that analysis showed that the characteristic tooth-shaped jags were created mostly at the centre of the cold crucible segments. In addition, experimental results are suitable for the numerical models validation and further investigation of the cold crucible design.
Electropolishing is electrochemical method used in metal working that has a vital role in production of medical apparatus, in food or electric industry. The purpose of this paper is to determine optimal current parameters and time required for conducting electropolishing process from the perspective of changes of surface microgeometry. Furthermore, effect of different types of mechanical working used before electropolishing on final surface state was evaluated by observation in changes of topography. Research was conducted on electrolytic copper and brass. Analysis of surface geometry and its parameters (Ra, Sa) was used as criterion describing efficiency of chemical electropolishing. Results of the experiment allow for current parameter optimization of electrochemical polishing process for selected non-ferrous alloys with preliminary mechanical preparation of the surface.
The work is a continuation of the research carried out on a high-temperature calorimeter solution type on alloys from Ni-Al-Cr system. Thanks to the construction innovation introduced by authors the device allows the determination of the formation enthalpy of alloys at ambient and elevated temperatures. Experiments described in this article were carried out at three temperatures: 873K, 996K and 1150K on the alloys of the chemical compositions from the Ni75Al25÷ Ni87Cr13section of the Ni-Al-Cr system. On the basis of changes in the enthalpy of formation with increasing chromium content of the alloys, points corresponding to places of phase boundaries γ′ / γ′+γ / γ in Ni-Al-Cr system were determined. A similar relationship was observed in previous studies of alloys from Ni75Al25÷Ni75Cr25section. For precise determination of these characteristic points a statistical model was applied
The work shows the results of examinations conducted to ascertain the influence of the working power of a vacuum induction crucible furnace (ICF) and a furnace with a cold crucible (CCF), on the surface area of liquid Al-Zn alloy molten within these devices. It was determined that the increase of the value of this parameter causes the increase of the liquid alloys surface area. In the case of smelting alloy inside a crucible furnace the increase of power from 8 to 22 kW causes the increase of liquid alloy surface from 88 to 155 cm 2 . For a furnace with a cold crucible, the power increase from 70 to 130 kW causes the increase of the alloy surface from 280 to 330.3 cm 2 . For all power values a larger increase in surface area was observed in crucible furnaces (around two times). In cases of cold crucible furnaces, this increase was around 20%. Additionally, based on the examination results the way in which the surface area of liquid alloy can intensify the undesirable process of zinc fuming away, was discussed. It has been demonstrated that the process of zinc elimination from the examined alloy is more intensive while using a cold crucible induction furnace.
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