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Kastelic S.,Institute for Foundry and Heat Treatment | Kastelic S.,University of Ljubljana | Tusek J.,University of Ljubljana | Klobcar D.,University of Ljubljana | And 2 more authors.
Materiali in Tehnologije | Year: 2013

Friction-stir-welding (FSW) technology has been growing since it was patented in 1991 at TWI. Since then the majorityof research and industrial applications for joining aluminium alloys were made on wrought aluminium alloys. Lately severalinvestigations have been done in FSW of dissimilar alloys. FSW also has a big potential in the casting industry - especially in high-pressure die casting (HPDC). In this article an investigation of a FSW dissimilar joint made from a casting aluminium alloy (AA413.0) and technically pure aluminium (AA1050) was done. This kind of joint can be used to make an assembled casting, joined with FSW with the aim to have a casting with different material properties or to join HPDC with FSW to assemble a casting with inner cavities. In this article the temperature distribution of the FSW joint of a cast aluminum alloy and technically pure aluminum is investigated. In the experimental work several FSW parameters were tested: the tool speed, the tool rotation and the position of the tool regarding the joint center. During joining the temperature was measured with a thermocouple and the temperature distribution in steady state was calculated with the FEM program Sysweld. The microstructure and mechanical properties of the joint were investigated.

Petrovic D.S.,Slovenian Institute of Metals And Technology | Medved J.,University of Ljubljana | Klancnik G.,University of Ljubljana | Klancnik G.,Institute for Foundry and Heat Treatment
Materiali in Tehnologije | Year: 2013

Thermodynamic arguments and calculations were used to describe a complete dissolution of a copper wire in a SnCu1 lead-free solder during hot-dipping at 400 °C. For the calculation of the phase diagram the newly reviewed Gibbs energies of the phases were used. The experimental investigation involved a visual inspection, stereomicroscopy, scanning electron microscopy (FE-SEM/EDX) and a thermal analysis (DSC). The results showed that the dissolution of the copper wire during hot dipping at a selected working temperature can be attributed to the increased solubility of the copper in the liquid solder and a prolonged time of dipping. Thus, the applied temperature was too high for the geometry, the volume-to-surface ratio, of the selected fuse element. Laboratory simulation tests performed at 303 °C showed a much slower kinetics for the Cu pick-up.

Strekelj N.,University of Ljubljana | Naglic I.,University of Ljubljana | Klancnik G.,Institute for Foundry and Heat Treatment | Nagode A.,University of Ljubljana | Markoli B.,University of Ljubljana
International Journal of Materials Research | Year: 2015

In this study we investigated the microstructural changes after a variety of heat treatments of the quasicrystalline Al - Mn - Be - Cu alloy. In addition, we report on Vickers microhardness measurements and tensile-test results for the same materials. The samples were produced in a conventional manner, i. e., melting in an electrical resistance furnace in air and a gravitational casting process using a round copper die, which was in the form of a tensile-test specimen with a diameter of 5 mm. After the casting, some of the samples were just solution treated (annealed) and then quenched in water, while others were additionally aged (artificially - T6, or naturally - T4) or directly aged after the casting. In comparison to the as-cast state, the Vickers microhardness values of the aluminum-based matrix and the tensile properties of the samples decreased when just the solution treatment, T4 or T6 treatment was performed. The tensile properties also decreased after the heat treatments. A microstructural inspection revealed that the microstructural changes occurred already during the solution treatment, i. e., the formation of the phases Be4Al(Mn,Cu) and τ1-Al29Mn6Cu4 on the approximant HAl4Mn and quasicrystalline i-phase particles' edges and the occurrence of precipitates in the αAl matrix. The precipitates that would additionally contribute to the hardening of the alloy did not form. The directly aged samples showed little or no increase in microhardness values in comparison to the as-cast samples, but possibilities of θ" precipitates being formed from the already saturated matrix after the casting could not be excluded. After all the heat treatments the quasicrystalline i-phase, as a primary and eutectic phase, was preserved. © Carl Hanser Verlag GmbH & Co. KG.

Petric M.,University of Ljubljana | Kastelic S.,University of Ljubljana | Kastelic S.,Institute for Foundry and Heat Treatment | Mrvar P.,University of Ljubljana
Journal of Mining and Metallurgy, Section B: Metallurgy | Year: 2013

The aim of this paper is the selections of proper electrode material for four-probe technique electrical resistivity measurement of aluminium and aluminium alloys. The biggest problem of electrodes is oxidation during measurement causing high contact resistance and giving wrong results. Various materials have been tested and aluminium electrodes have been chosen. Advantage of aluminium electrodes is that they are melted in specimen right after the pouring and causing no interface which is resulting with any contact resistance. The device together with measuring cell for "in situ" measurement of electrical resistivity was developed using four-probe DC technique.

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