Abstract
The dissolution of Mn and Fe in liquid Al presents a challenge due to their high melting points and low diffusivity. A literature review reveals that the existing knowledge of the processes involved in the dissolution of both Fe and Mn in liquid Al is rather ambiguous. Thus, this work aimed to obtain more detailed insights into the dissolution behavior of Mn and Fe in various Al melts. The results of the Mn dissolution tests showed that three intermediate phases were involved in the dissolution process, all of which exhibited a smooth interface between Mn and the liquid. These three phases were identified as the γ2, Al11Mn4, and µ phases which grow slowly, penetrating the Mn particles. The results of the Fe dissolution tests showed that in pure Al, the Al5Fe2 phase dominates the dissolution process and penetrates the Fe particles. The addition of Ti into the molten Al alters the intermetallic compound formation by replacing Al5Fe2 by Al2Fe. The addition of Si significantly inhibited the Fe dissolution kinetics. A theoretical approach based on Ficks’ law was used to explain the experimentally obtained Mn and Fe dissolution rates. It showed that the surface area and shape of the additives significantly affected the dissolution processes.
Highlights
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
The highest dissolution rate was for the compact with 80 pct Mn-containing flux
The second highest dissolution rate was obtained for the non-fluxed 80 pct Mn compact which showed a similar trend as the dissolution of the fluxed compact
Summary
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. During the incubation period, the aluminum inside the compact starts to melt. The Al melt reacts with the alloying-element particles exothermally to form various intermetallic compounds. The compact is disintegrated and disperses into the melt for further dissolution.[3,4]. 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] 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
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