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Goral A.,Polish Academy of Sciences | Berent K.,AGH University of Science and Technology | Nowak M.,Institute of Non Ferrous Metals Gliwice | Kania B.,Polish Academy of Sciences
Archives of Metallurgy and Materials

The study presents investigations of an influence of various direct current densities on microstructure, residual stresses, texture, microhardness and corrosion resistance of the nickel coatings electrodeposited from modified Watt's baths. The properties of obtained coatings were compared to the nano-crystalline composite Ni/Al2O3 coatings prepared under the same plating conditions. The similarities and differences of the obtained coatings microstructures visible on both their surfaces and cross sections and determined properties were presented. The differences in the growth character of the Ni matrix and in the microstructural properties were observed. All electrodeposited Ni and Ni/Al2O3 coatings were compact and well adhering to the steel substrates. The thickness and the microhardness of the Ni and Ni/Al2O3 deposits increased significantly with the current density in the range 2 - 6 A/dm2. Residual stresses are tensile and they reduced as the current density increased. The composite coatings revealed better protection from the corrosion of steel substrate than pure nickel in solution 1 M NaCl. Source

Goral A.,Polish Academy of Sciences | Nowak M.,Institute of Non Ferrous Metals Gliwice | Berent K.,Polish Academy of Sciences | Kania B.,Polish Academy of Sciences
Journal of Alloys and Compounds

Electrodeposition process is a very promising method for producing metal matrix composites reinforced with ceramic particles. In this method insoluble particles suspended in an electrolytic bath are embedded in a growing metal layer. This paper is focused on the investigations of the nickel matrix nanocomposite coatings with hard α-Al2O3 nano-particles, electrochemically deposited from modified Watts-type baths on steel substrates. The influence of various current densities on the microstructure, residual stresses, texture, hardness and corrosion resistance of the deposited nickel/alumina coatings was investigated. The surface morphology, cross sections of the coatings and distribution of the ceramic particles in the metal matrix were examined by scanning electron microscopy. The phase composition, residual stresses and preferred grain orientation of the coatings were characterized using X-ray diffraction techniques. The coating morphology revealed that α-Al2O3 particles show a distinct tendency to form agglomerates, approximately uniformly distributed into the nickel matrix. © 2014 Elsevier B.V. All rights reserved. Source

Goral A.,Polish Academy of Sciences | Nowak M.,Institute of Non Ferrous Metals Gliwice | Wojewoda-Budka J.,Polish Academy of Sciences
Solid State Phenomena

Our interests are focused on the Ni/Al2O3 nanocomposite coatings electrochemically deposited in modified Watt's-type baths into which α-Al2O3 nanopowder is added on steel substrates. The effect of different amounts of α-Al2O3 phase in the electrolyte baths on microstructure of electrodeposited Ni/Al2O3 coatings is investigated. In order to study the coatings the non-destructive X-ray diffraction techniques are applied. As indirect techniques, they are supported by imaging methods, especially scanning electron microscopy. © (2013) Trans Tech Publications, Switzerland. Source

Milenin A.,AGH University of Science and Technology | Gzyl M.,AGH University of Science and Technology | Rec T.,AGH University of Science and Technology | Plonka B.,Institute of Non Ferrous Metals Gliwice
Archives of Metallurgy and Materials

Mathematical model of small-diameter wires extrusion from biocompatible MgCa08 (Mg - 0.8% Ca) magnesium alloy was developed in the current paper in order to determine window of allowable technological parameters. Compression and tensile tests were carried out within temperature range 250-400°C and with different strain rates to determine the fracture conditions for the studied alloy. Finite element (FE) analysis was used to predict the billet temperature evolution and material damage during processing. The extrusion model takes into account two independent fracture mechanisms: a) surface cracking due to exceeding of the incipient melting temperature and b) utilization of material formability. FE simulations with different initial billet temperatures and pressing speeds were performed in order to determine the extrusion limit diagram (ELD) for MgCa08 magnesium alloy. The developed ELD was used to select the parameters for the direct extrusion of wires with diameter of 1 mm. Then, the extrusion of twelve wires was conducted at 400°C with pressing speed 0.25 mm/s. It was reported that the obtained wires were free from defects, which confirmed the good agreement between numerical and experimental results. Source

Jurcius A.,Vilnius Gediminas Technical University | Valiulis A.V.,Vilnius Gediminas Technical University | Cernasejus O.,Vilnius Gediminas Technical University | Kurzydlowski K.J.,Warsaw University of Technology | And 2 more authors.
Journal of Vibroengineering

The welding process can join two similar materials with a bond that has mechanical properties comparable to the original material. Unfortunately, this process induces residual stresses in the weldment, which, if left untreated, can cause distortion of the part, premature fatigue failure or cracking along the weld. A post-weld heat treatment is the traditional method of relieving these stresses, but is costly and a time consuming process. Heat treatment is required for weldments, which have heavy fatigue loading since the post-weld heat treatment reduces the residual stresses in the weldment and generates more uniform mechanical properties. Vibratory stress relief (VSR) techniques could be used to substitute the heat treatment for these types of weldments and save time and money. The purpose of this paper is to provide a brief overview of the generation, measurement, and reduction of residual stresses. Residual stresses in the weld bead were measured by means of X-ray diffraction, ultrasonic technique and hole drilling methods. In addition, welded specimens were subjected to mechanical testing with purpose of determination of VSR effect on weld and heat-affected zone metal. © Vibromechanika. Journal of Vibroengineering. Source

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