Aluminium alloys are characterized by a low density, acceptable mechanical properties and good technological properties. This unique connection of features made aluminium alloys perfect structural material for the transportation industry. Also, due to their good electrical conductivity they also found application in energy production industry. High mechanical properties and electrical conductivity of the Al-Si alloys with Mg addition may be achieved by heat treatment. However, the highest mechanical properties are achieved in the early stages of age hardening - due to precipitation of coherent phases, while high electrical conductivity may be achieved only by prolonged aging, during precipitation of semi-coherent or fully noncoherent, coarse phases. Carefully heat treated AlSi7Mg alloy may exhibit both fairly high electrical conductivity and slightly increased mechanical properties. The following article present results of the research of influence of heat treatment on the properties and microstructure of sand cast AlSi7Mg alloy. Microstructure observations were performed using light microscopy, scanning electron and scanning-transmission electron microscopy. Hardness and electrical conductivity of the AlSi7Mg alloy were investigated both in as-cast condition and after heat treatment. Maximum hardness of the alloy is achieved after solutioning at 540°C for 8h, followed by 72h of aging at 150°C, while maximal electrical conductivity after solutioning at 540°C for 48h, followed by 96h of aging at 180°C. Increase of the electrical conductivity is attributed to increasing distance between Si crystals and precipitation of semi coherent phases.
Ł. Poloczek, B. Dybowski, K. Rodak, R. Jarosz and A. Kiełbus
K. Dybowski, J. Sawicki, P. Kula, B. Januszewicz, R. Atraszkiewicz and S. Lipa
This paper presents a comparison of the deformations and residual stresses in gear wheels after vacuum carburizing process with quenching in high-pressure nitrogen and oil. The comparison was made on a medium-sized gear wheels, made of AMS6265 (AISI 9310) steel. This steel is applied in the aerospace industry for gears. The study has provided grounds for an assessment of the effect of the method of quenching on the size of deformations. Compared to oil quenching, high-pressure gas quenching following vacuum carburizing resulted in more uniform and smaller deformations.
P. Kula, W. Szymański, Ł. Kołodziejczyk, R. Atraszkiewicz, K. Dybowski, J. Grabarczyk, R. Pietrasik, P. Niedzielski, Ł. Kaczmarek and M. Cłapa
In this work, the growth mechanisms of chemical vapor deposited and metallurgical graphene and their selected mechanical and electrical properties were investigated. The study revealed the influence of the growth mechanisms on monoand poly-crystalline nanostructures of synthesized graphene monolayers. The structure of flake boundaries greatly affects both the mechanical and electrical properties. The key factors are overlapping of the graphene flakes, their degree of mismatch and the presence of π type bonds. All of these issues should be taken into account when developing industrially scaled technologies for graphene manufacturing.
M. Cecotka, K. Dybowski, L. Klimek, S. Lipa, A. Rylski, D. Sankowski, R. Wojciechowski and M. Bąkała
Abrasive blasting is one of the methods of surface working before hot-dip zinc-coating. It allows not only to remove products of corrosion from the surface, but it also affects the quality of the zinc coating applied later, thereby affecting wettability of surface being zinc-coated. The surface working can be done with different types of abrasive material.
The paper presents an effect of the method of abrasive blasting on wetting the surface of steel sheets by liquid zinc. Steels sheets following blasting with Al2O3 of different granularity and shot peening were examined. The worst wetting was recorded for a sample following shot peening - the results are below those for the reference test conducted for a sample not previously subjected to any treatment. Samples following abrasive blasting have similar parameters, regardless of the size of grain used for the treatment.