Materials Science and Engineering A 460–461 (2007) 561–573 Effects of individual and combined additions of Be, Mn, Ca and Sr on the solidification behaviour, structure and mechanical properties of Al–7Si–0.3Mg–0.8Fe alloy S.S. Sreeja Kumari, R.M. Pillai ∗ , T.P.D. Rajan, B.C. Pai Regional Research Laboratory (CSIR), Thiruvananthapuram 695019, Kerala, India Received 17 May 2006; received in revised form 20 January 2007; accepted 22 January 2007 Abstract The effects of individual and combined additions of Be, Mn, Ca and Sr on the solidification, structure and mechanical properties of Al–7Si–0.3Mg–0.8Fe alloy has been investigated. Thermal analysis study shows that all additions except Be show a peak corresponding to -Fe intermetallic phase formation. Ca and Sr additions decrease the eutectic temperature (by 6.6 and 8.7 K, respectively) compared to the untreated alloy and lead to modification of eutectic Si from platelet to fibrous form. The peak corresponding to Be–Fe phase has been identified by DTA. Mn (0.4%) and Be (0.2%) additions to Al–7Si–0.3Mg–0.8Fe alloy change the morphology of platelet -phase to script form leading to significant improvement in tensile and both tensile and impact properties, respectively. Addition of Be, Ca and Sr to Mn added Al–7Si–0.3Mg–0.8Fe alloy improves the impact strength significantly due to the modification of the eutectic Si from acicular to fibrous form and refinement of platelet -phase in addition to its morphological change from platelet to Chinese script form. Combined additions of Be + Mn, Ca + Mn and Sr + Mn result in a reduction in the impact strength compared to individual additions of Be, Ca and Sr. The best combinations of both tensile and impact properties have been obtained with the combined additions of Be + Mn, Ca + Mn and Sr + Mn to Al–7Si–0.3Mg–0.8Fe alloy. A trace amount of Be (0.005%) addition to Ca and Sr leads to superior tensile properties compared to individual additions of Ca and Sr. © 2007 Elsevier B.V. All rights reserved. Keywords: Al–7Si–0.3Mg alloy; Fe intermetallics; Beryllium; Manganese; Calcium; Solidification 1. Introduction Cast Al–Si alloys find widespread applications especially in the automotive and aircraft industries due to their excel- lent combination of both casting characteristics and mechanical properties. Over the years, these alloys have been specially developed to meet the increasing demands of today’s industry, which has resulted in the production of smaller and light-weight components to comply with property, environmental and other specifications [1]. Recently, appeal for recycling of resources is becoming more and more intensive with increasing pub- lic awareness on conservation of materials and energy and protection of environment. However, the increasing use of recy- cled aluminium casting alloys warrants strict process control to remove the ill effects of impurity elements [2]. ∗ Corresponding author. Tel.: +91 471 2515270; fax: +91 471 2491712. E-mail address: rmpillai@rediffmail.com (R.M. Pillai). Iron is the most common and harmful impurity in cast alu- minium alloys forming platelet form of iron intermetallic phase (), which is detrimental to the mechanical properties and frac- ture toughness. Aluminium foundry alloys always contain a certain quantity of iron. In addition, it is sometimes unintention- ally added to the molten metal by various means, particularly through the dissolution of the iron tools often used during melt- ing and casting. The raw materials such as aluminium and silicon used for the preparation of alloys also contain a certain unavoid- able amount of iron [3,4]. In order to achieve the best mechanical properties, either the Fe content has to be maintained as low as possible or the size, shape and distribution of intermetallic compounds should be modified. Among the various methods available to neutralize the ill-effects of iron, neutralization by adding trace elements [5] is commonly practiced. Be has been found to be the most effective element in improving the mechanical properties of Al–Si–Mg alloys [6–9]. However, Be is carcinogenic. Manganese is the most commonly used and the least expensive element for Fe neutralization in 0921-5093/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2007.01.082