Morphological studies on $\beta-FeSiAI_5$ phase in AI-7Si-0.3Mg alloy with trace sdditions of Be, Mn, Cr, and Co

Murali, S and Raman, KS and Murthy, KSS (1994) Morphological studies on $\beta-FeSiAI_5$ phase in AI-7Si-0.3Mg alloy with trace sdditions of Be, Mn, Cr, and Co. In: Materials Characterization, 33 (2). pp. 99-112.

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Abstract

Although the detrimental effect of iron on the mechanical properties of A1-7Si-0.3Mg alloy has been well established, studies on neutralizing this effect have been very few and in- conclusive. The $\beta$-phase $(FeSiAl_5)$, seen in the interdendritic areas in the form of needles/plates, is responsible for this effect. In the present study, it has been observed that trace additions of Be, Cr, Mn, and Co, individually or combined, will tie up Fe to form new phases with altered morphologies such as Chinese scripts, polygons, stars, and irregular shapes. Cr-Fe and Mn-Fe phases are seen both in interdendritic regions and inside the a-A1 dendrites, while Co-Fe phase is mostly seen inside the a-A1 dendrites. However, Be-Fe phase is observed only inside the ~-A1 dendrites. Empirical formulas have been de- veloped from wavelength dispersive analysis on these relatively new Fe phases with trace additions. At higher Fe levels (0.8-1%) and with Be trace addition, individually or combined with Mn and Cr, fractographs reveal pyramids surrounded by cells, while other trace additions such as Mn, Cr, and Co reveal brittle cleavage fracture. All Be-added alloys, individually and combined with Mn and Cr additions, appear to neutralize the detrimental effect of Fe content on mechanical properties.

Item Type:	Journal Article
Publication:	Materials Characterization
Publisher:	Elsevier
Additional Information:	Copyright of this article belongs to Elsevier.
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	18 Oct 2006
Last Modified:	19 Sep 2010 04:31
URI:	http://eprints.iisc.ac.in/id/eprint/8271

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