Friction stir welding for marine applications : mechanical behaviour and microstructural characteristics of Al-Mg-Si-Cu plates

Friction stir welding is a multipurpose solid-state joining process mainly used for aluminium and steel plates and frames. Friction stir welded non-ferrous metallic alloys, similar or dissimilar, in particular aluminium alloys, provide opportunities for the improvement and developement of new product designs. This paper investigates the correlation between the mechanical behaviour and morphological structures of friction stir welded Al-Mg-Si(Cu) alloy plates in two temper conditions. Micro Vickers hardness and tensile tests were carried out. Additionally, morphology was investigated using optical microscopy and scanning electron microscopy. Samples subjected to the post weld heat treatment were shown to have the best properties owing to the formation of a significant number of hardening particles which, added to the nugget grain refinement, resulted in the increase of the material strength

Friction stir welding for marine applications : mechanical behaviour and microstructural characteristics of Al-Mg-Si-Cu plates

Friction stir welding is a multipurpose solid-state joining process mainly used for aluminium and steel plates and frames. Friction stir welded non-ferrous metallic alloys, similar or dissimilar, in particular aluminium alloys, provide opportunities for the improvement and developement of new product designs. This paper investigates the correlation between the mechanical behaviour and morphological structures of friction stir welded Al-Mg-Si(Cu) alloy plates in two temper conditions. Micro Vickers hardness and tensile tests were carried out. Additionally, morphology was investigated using optical microscopy and scanning electron microscopy. Samples subjected to the post weld heat treatment were shown to have the best properties owing to the formation of a significant number of hardening particles which, added to the nugget grain refinement, resulted in the increase of the material strength

Dielectric and ferroelectric properties of BST ceramics obtained by a hydrothermally assisted complex polymerization method

Ba0.8Sr0.2TiO3 (BST) powder, obtained by a hydrothermal treatment of precursor solution previously prepared by a complex polymerization method (HT-CPM), was uniaxially pressed and sintered at 1280 degrees C for 1-32 h. The sintering effect on structural parameters, phase composition, dielectric and ferroelectric properties was investigated. Rietveld refinement analysis of BST ceramics showed that predominant phase was tetragonal BST with monoclinic Ba6Ti17O40 (B6T17) as a secondary phase. Phase contents determined by Rietveld refinement match well with the results of energy dispersive X-ray analysis. Dielectric and ferroelectric properties of BST ceramics have been correlated with density of sintered compacts, phase composition, structural parameters and microstructure. The sample sintered for 16 h showed the highest density (93% rho(t)), as well as the highest value of dielectric constant (similar to 2300) and remanent polarization - Pr (2 mu C/cm(2)) among investigated samples