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The effect of process parameters on residual stress in a friction stir processed cast aluminium alloy AlSi9Mg

Węglowski M. S., Sędek P., Hamilton C.

Engineering Transactions

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2016

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Vol. 64, iss. 3

301--309

EN

The effect of friction stir processing (FSP) on residual stress in a modified cast aluminium alloy AlSi9Mg is presented. The influence of rotational speed and tool type were analysed. The trepanation method was utilized to experimentally measure the residual stress. The results indicate that an increase in rotational speed causes an increase in residual stress. The region around the FSP bead was characterised by tensile residual stress fields which were balanced by compressive stresses in the parent material. A higher residual stress was observed on the advancing side than on the retreating side. Moreover, this asymmetry in residual stress distribution is due to the asymmetry in the volume of material plasticized along the advancing and retreating sides of the stir zone, generating the observed heat distribution. A higher level of residual stress was achieved with the Triflute tool than with a conventional tool.

2

Characteristics of AlSi9mg/2017A Aluminum Alloys Friction Stir Welded with Offset Welding Line and Root-Side Heating

Mroczka K.

Archives of Metallurgy and Materials

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2014

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Vol. 59, iss. 4

1293--1299

EN

Welding of materials differing significantly in terms of chemical composition and microstructure is one of the main advantages of the Friction Stir Welding method. This paper presents the results of welding of a cast AlSi9Mg (hypoeutectic silumin) and 2017A aluminum alloys. The welding was performed with a high linear velocity (over 1 m/min). The modification of the process consisted in offsetting the welding line toward the advancing side, and in on application of an additional heat source from the root side. The study of the macrostructure (with high resolution of the image) revealed the presence of defects in the weld, despite greater plasticity of the material results from raising the temperature. The analysis (by SEM, SEM-EDS) of constituent stable phases within the cast alloy, showed their considerable fragmentation, however to a various degree. The material above the weld nugget was not mixed and contained micro-defects that did not result from the welding. The hardness distribution within the weld nugget, reveals slight strengthening of the both cast and wrought alloys. A metastable state of the 2017A alloy was also documented, however, the alloy hardness increased within the weld nugget due to the natural aging. On the other hand, the hardness of the heat-affected zone in this alloy does not increase also due to the natural aging.

PL

Jedną z głównych zalet technologii FSW jest zdolność do spajania materiałów znacznie różniących się składem chemicznych. W artykule przedstawiono rezultaty zgrzewania stopów aluminium AlSi9Mg (silumin podeutektyczny) i 2017A. Zgrzewanie wykonano z dużą prędkością liniową (powyżej 1 m/min). Proces zgrzewania zmodyfikowano przesuwając linię zgrzewania w kierunku strony natarcia oraz stosując dodatkowe źródło ciepła od strony grani. Badania makrostruktury zgrzeiny wykazały obecność wad mimo zwiększonej plastyczności materiału podczas zgrzewania, w wyniku podwyższenia temperatury. Podczas zgrzewania FSW dochodzi do fragmentacji cząstek w obszarze działania narzędzia. Na podstawie badań SEM i SEM-EDS wykazano różny stopień fragmentacji wydzieleń w stopie AlSi9Mg. Badania wykazały ponadto ograniczoną intensywność mieszania materiału przez narzędzie w strefie nad jądrem zgrzeiny. W tym obszarze wystepują również niewielkich rozmiarów wady, niebędące efektem płynięcia materiału. Z kolei analizy rozkładów twardości na przekroju porzecznym zgrzeiny dowiodły niewielkiego umocnienia stopu odlewniczego. Natomiast stop 2017A, w obszarze jądra zgrzeiny, wykazał niestabilność mikrostruktury (bezposrednio po zgrzewaniu) oraz uległ umocnieniu w wyniku starzenia naturalnego. Starzeniu nie uległ obszar strefy wpływu ciepła.

3

Effect of applied pressure on the quality of squeeze cast parts made from AlSi9Mg alloy

Reguła T., Sobczak J. J., Fajkiel A., Dudek P.

Archives of Foundry Engineering

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2011

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Vol. 11, iss. 3

55-60

EN

The results of the study of an influence of pressure in the direct squeeze casting process on the physical and mechanical properties of an AlSi9Mg alloy are presented. The specimens were made by casting the tested AlSi9Mg alloy under the conditions of variable squeeze pressure, using a PHM 160c type hydraulic press. Analyzing the results of the experiment, it has been found that, the applied pressure has an important impact on the quality of castings squeezed in liquid state. The effect of squeeze pressure proves the advisability of continuing the application of various liquid-phase methods using external pressure to improve the properties of castings produced.