Ultrasonic welding is very useful for joining thin metal sheets [1, 2]. The effect of ultrasound on microstructure is currently not well understood because the changes produced depend very much on the welding parameters and the properties of the metal being considered. Thin sheets formed by cold rolling acquire a special grain structure. During the welding process the heat produced causes recrystallization; even where heat is not applied in the joining process the recrystallization process alters the mechanical properties within the heat affected zone (HAZ). The mechanical properties of the welded samples depend on the microstructure. In this work we analyse the ultrasonic welding effect on the joint and the HAZ [3, 4].
The wide use of composite materials is mainly due to their excellent strength / mass ratio, corrosion resistance and relatively low price. Approximately 35-40% of the fibre-reinforced composites are made of thermoplastic polymers in which fibreglass, carbon or natural fibres are most often used as reinforcement, while the remaining 60 – 65% is made up of high-tech carbon or glass fibre-reinforced thermosetting composites. Most of them are used in the transport and electronics industries. New processing technologies not only improve the properties of the products but also contribute to reducing costs.
In this paper, we compare the results of mechanical tests with molded standard specimens with polypropylene matrix and test results from cut-outs from injection molded products.
Mária Dománková, Marek Adamech, Jana Petzová, Katarína Bártová and Peter Pinke
Borated austenitic stainless steel is used in nuclear industry due to the high neutron absorption efficiency. The plasma, laser and electron beam welding experiments were used for the study of the weld joints microstructure. The microstructure changes caused by welding process were observed by light optical microscopy and transmission electron microscopy. The microstructural characterization and microchemical analysis showed significant changes of the phase composition in the weld metal mainly. The austenitic dendrites were surrounded by eutectics, which were the mixture of the M2(C,B) and M23(C,B) borocarbides, δ-ferrite and austenite.