Browsing by Author "Dutkiewicz, Jan Marek"

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Access status: Open Access ,
Mikrostruktura i własności połączeń stopów aluminium wykonanych metodą zgrzewania tarciowego z mieszaniem materiału spoiny
(Data obrony: 2010) Kalemba, Izabela
Wydział Inżynierii Metali i Informatyki Przemysłowej
The alloy 7136 belongs to the $Al-Zn-Mg-Cu$ age hardenable class of aluminum alloys. These alloys offer very good properties, i.e. high strength and simultaneously good corrosion resistance. Thanks to these properties $Al-Zn-Mg-Cu$ alloys are very attractive to aerospace applications. However application of these alloys is limited due to problems associated with their welding. $Al-Zn-Mg-Cu$ alloys are classified as non-weldable. The aim of the PhD work is characterization of quality and properties of friction stir welded 7136-T76 extrusions. FSW is a novel solid-state joining process. During the process the material is mixed and undergoes intense plastic deformation accompanied by a temperature increase. This research addresses the detailed investigation microstructure, mechanical properties and corrosion resistance of FSW welds. These studies demonstrated that friction stir welding applied to the $Al-Zn-Mg-Cu$ alloys produces high quality, sound welds. The FSW joints are fundamentally defect-free and display high mechanical properties and good corrosion resistance. The performed investigations show relatively large range of process parameters, which allow to obtain good quality of welds, both in respect of microstructure and properties. The applied tool rotation speeds do not have influence on quality welds.
Access status: Restricted ,
Określenie wpływu dodatku manganu i krzemu na warunki odkształcenia superplastycznego mosiądzów $\alpha + \beta$
(Data obrony: 2009) Malczewski, Piotr
Wydział Metali Nieżelaznych
The paper presents results of influence of manganese additions up to 11 wt. $\%$ and silicon up to 1 wt. $\%$ for superplastic properties of $\alpha + \beta$ brasses. The thermomechanical treatment consisted of hot rolling, quenching from the P range, cold rolling and annealing. It resulted in grain refinement down to $10 \mu m$. The tensile tests were conducted at various rates and temperatures in therange $400-600^{\circ}C$ in order to determine the strain rate sensitivity coefficient $m$. It was done using step strain rate change.The increase of additions of manganese up to 11 wt.$\%$ improved superplastic properties and decreased deformation temperature. Alloys containing 4,5 wt. $\% Mn$ showed best superplastic properties, where the value of strain rate sensitivity coefficient $m$ attained maximum values $m=0,6$. Alloys containing 11 wt.$\% Mn$ showed decrase of strain rate sensitivity down to $m= 0,55$ and temperature range of $450-500^{\circ}C$. Texture studies using OIM indicated presence of a very weak texture within a phase after grain refinement treatment and development of a brass type texture after superplastic deformation within a phase. This indicate participation of crystallographic slip deformation in addition to grain boundary sliding. Author describes also deformation by gas pressure, to a shape of hemisphere. It was attained in one operation corresponding to $82\%$ deformation from the mutual sheets.