On the Dissolution Process of Manganese and Iron in Molten Aluminum
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CTION
THE alloying elements Mn and Fe can be added into an Al melt either as discrete particles or as powder compacts of master alloys consisting of various fractions of the alloying element and aluminum.[1,2] The dissolution of compacts occurs in three steps. First, during the incubation period, the aluminum inside the compact starts to melt. Next, the Al melt reacts with the alloying-element particles exothermally to form various intermetallic compounds. Eventually, the compact is disintegrated and disperses into the melt for further dissolution.[3,4] Mn and Fe are important alloying additions for industrial Al alloy production. However, achieving complete dissolution of these elements in liquid Al has been a challenge owing to their high melting temperatures and low solid solubilities (0.05 and 1.8 wt pct,[5,6] respectively). Common issues in many cast houses are low dissolution rates and low recovery.[1,4] In fact, the dissolution of these alloying elements involves the formation of intermetallic phases. The formation and growth of these phases at the interface between the solid GHADIR RAZAZ and TORBJO¨RN CARLBERG are with the Department of Natural Science, Mid Sweden University, 851 70, Sundsvall, Sweden. Contact e-mails: [email protected]; [email protected] Manuscript submitted October 29, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
additives and liquid metal are governed by complex diffusion conditions.[7] Several studies have been performed focusing on the dissolution of Fe.[5,7–10] However, the dissolution of Mn in Al melt has not been investigated to the same extent. Nevertheless, in a previous work, the dissolution behavior of both Fe and Mn in Al melts has been addressed.[1] It was shown that the morphology of the intermetallic compounds formed at the interface of solid Fe in liquid Al differs from that of the phases formed at the interface of solid Mn. It was observed that during Fe dissolution the intermetallic phases grow towards the solid Fe forming an irregular interface, while during Mn dissolution, the intermetallic phases grow outwards into the liquid Al matrix forming a smooth interface.[1] During Fe dissolution, Al5Fe2 and Al3Fe were detected as the major and minor intermetallic phases, respectively, during Fe dissolution.[7–9] Meanwhile, during Mn dissolution, Al4Mn (l) was the only observed intermetallic phase.[1] Although the types of interfacial phases formed, their morphology, and thickness influence the dissolution rate and alloying yield,[8,9] a literature review shows that no detailed description of the dissolution process of Fe and Mn in liquid Al exists, which urges the clarification of these processes. The purpose of this work is to improve the understanding of the dissolution process of Mn and Fe in liquid Al. Thus, its aim is to study the phase formations at the interfaces, the related interface morphologies, growth kinetics, and dissolution rates.[8,9] Dissolution
experiments have been performed with various Mn compacts and pure Fe additives in Al liquid. These exp
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