INFLUENCE OF IRON AND MANGANESE ON STRUCTURE AND MICROPOROSITY OF THE DC CAST AA5083 ALLOY Carmen Stanica 1 , Petru Moldovan 2 , Gheorghe Dobra 1 , Dionezie Bojin 2 , Sorin Dimitriu 2 1 ALRO SA, 116 Pitesti Street, 230104, Romania Slatina 2 Politehnica University of Bucharest, 313 Spl.Independentei, Romania Keywords: Aluminum alloys, Microstructure, Microporosity. Abstract The AA5083 alloy is one of the most common alloys in the AA5xxx series wrought aluminum alloys. The effect of iron and manganese content on the microstructure and microporosity has been studied by optical microscopy (OM), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis. It was clear underlined that micropores are well connected with iron- and manganese intermetallics, which cause blockage in the interdendritic channels, which hinder feeding and hence promote microporosity of DC cast alloys. Introduction Aluminum alloy AA5083 is known for exceptional performance in extreme environments. It is highly resistant to attack by both seawater and industrial chemical environments. AA5083 alloy also retains exceptional strength after welding. DC casting of AA5083 alloy results in a range of cooling rates in various zones of the casting. It is therefore essential to control the microstructure evolution during solidification, to prevent defects in casting. The aluminum-magnesium commercial alloys contain varying amounts of impurity elements such as iron, silicon, zinc, calcium, and sodium. The impurities and alloying elements partly go into solid solution in the matrix and partly form intermetallic particles during the solidification process. Iron is the most deleterious impurity element in cast aluminum alloys due to its role in the formation of the brittle compound (- AlFeSi) at cooling rates normally employed in permanent mold casting [1]. This compound tends to form thin platelets appearing as needles in cross section, which are very hard and brittle and have a relatively low bond strength with the matrix. The detrimental effect of iron can be minimized by manganese addition, rapid solidification or melt superheating [1]. The manganese addition is the most common addition to neutralize the effects of iron, although other metals such as chromium, cobalt, molybdenum and nickel can also be used, with less success [2,3]. The addition of manganese basically expands the -phase region, and thus, crystallization of -phase (Chinese script morphology) is possible even at high iron contents [4]. The purpose of the present paper is to study the influence of iron and manganese on the microstructure and microporosity of as-cast AA5083 alloy in different casting conditions. Experimental procedure Both foundry and laboratory experiments were done in this study. Foundry experiments were conducted at Aluminum Plant, SC ALRO SA Slatina, Romania. The laboratory experiments were performed at the Testing of Materials Quality Laboratory at Polytechnic University of Bucharest and the Metallography laboratory of SC ALRO SA Slatina. Foundry experiments 5083 alloy was performed in a gas furnace at ALRO Slatina, with a slightly oxidant flame. After elaboration, the melt was “in line” degassed with Ar+Cl 2 in ALPUR TS 35-24 installation and filtered through ceramic foam filters. The slabs were cast in Pechiney installation. The chemical composition of the 5083 alloy is shown in table I and slab’s casting parameters are presented in table II. Table I. Composition of 5083 alloy, wt.% Charge Cu Fe Si Mn Mg Zn Cr Ti Ca Na 1-S28030337 0.045 0.270 0.370 0.66 4.63 0.053 0.067 0.022 0.0130 0.0006 2-S28050494 0.040 0.250 0.170 0.65 4.50 0.070 0.095 0.030 0.0020 0.0003 3-S28050496 0.040 0.267 0.130 0.63 4.58 0.030 0.100 0.030 0.0015 0.0002 4-S28050518 0.033 0.200 0.160 0.66 4.58 0.031 0.096 0.033 0.0010 0.0002 5-S28050519 0.086 0.200 0.207 0.70 4.70 0.048 0.092 0.038 0.0022 0.0006 6-S28050520 0.025 0.210 0.150 0.64 4.52 0.033 0.092 0.039 0.0025 0.0004 823 Light Metals 2009 Edited by: Geoff Bearne TMS (The Minerals, Metals & Materials Society), 2009 Light Metals 2009 Edited by: Geoff Bearne TMS (The Minerals, Metals & Materials Society), 2009