J. Mater. Sci. Technol., 2011, 27(7), 615-627. Solidification Studies of 3003 Aluminium Alloys with Cu and Zr Additions Majed M.R. Jaradeh and Torbjorn Carlberg † Mid Sweden University, FSCN, SE-851 70 Sundsvall, Sweden [Manuscript received December 23, 2010, in revised form March 9, 2011] The effects of Cu and Zr additions, on the microstructure formation, precipitation and ingot cracking, in commercial 3003 Al alloys have been studied. The investigation was carried out by characterizing the grain structure in DC-cast rolling ingots, and studying the solidification microstructure of Bridgman directionally solidified samples. To better understand the influence of the different Cu and Zr contents on the phase precipitations, differential thermal analysis (DTA) experiments were performed. Results from the ingot mi- crostructure analysis show that in commercial alloys with relatively high contents of Cu and Zr, no significant differences in measured grain sizes compared to conventional 3003 Al alloys could be found. However, only Zr containing alloys exhibited significantly larger grain sizes. Increased grain refiner and/or titanium additions could compensate for the negative effects on nucleation normally following Zr alloying. Different types of pre- cipitates were observed. Based on DTA experiments, increased Cu and Zr contents resulted in the formation of Al2Cu phase, and increased solidification range. It was also found that increased Mn content favors an early precipitation of Al 6 (Mn,Fe) giving relatively coarse precipitates. It was concluded that the Cu alloying has a detrimental effect on hot tearing. KEY WORDS: Aluminium 3003; Al-Cu-Zr alloys; Microstructure analysis; Directional solidifi- cation; Differential thermal analysis (DTA); Cracking; Hot tearing; Precipitation 1. Introduction Due to the need for aluminium heat transfer alloys with excellent thermal efficiency, high strength and corrosion resistance, the development of new alloys is continuously progressing. The commercial 3003 Al alloy (Al-Mn series) is the material that is pre- ferred for applications in heat-exchangers in the au- tomotive industry, as material for tubes and fins after subsequent brazing. This alloy type is generally not heat treatable, and the primary strengthening mech- anism is solid solution strengthening. One approach to improve the specific properties of an alloy is to add specific amount of different alloying elements, allow- ing for solid solution strengthening. Previous work has been performed on this alloy type, to study the † Corresponding author. Prof.; Tel.: +46 60 148751; Fax: +46 60 148875; E-mail address: torbjorn.carlber@miun.se (T. Carlberg). effect of additions of Zn, Si and Ti, to modify its structure and properties [1–4] . In the present work, the effects of Cu and Cu+Zr additions to the com- mercial 3003 Al alloy are studied. Small Zr additions are known to give effects of increasing strength, sag resistance and coarsening the grains to retard high- temperature deformation [5] . Cu is a hardening ele- ment, and its additions to 1.0 wt% improves strength after brazing, but decreases corrosion resistance, and above 1.1 wt%, coarse intermetallic compounds are formed during casting, which damage the homogene- ity of the metal and constitute initiation sites for corrosion [6] . With regard to the role of copper in cor- rosion resistance, the most recent work shows rather a favorable influence, while the copper remains in solid solution [7] . The elements Fe, Si, Cu, Zr and Ti, added to Al– Mn alloys in different amounts are known to have strong influence on the precipitation behavior [8] . Fe