Journal of Materials Processing Technology 210 (2010) 1754–1766 Contents lists available at ScienceDirect Journal of Materials Processing Technology journal homepage: www.elsevier.com/locate/jmatprotec Machinability aspects of new Al–Cu alloys intended for automotive castings E.M. Elgallad a , F.H. Samuel a,b,∗ , A.M. Samuel a , H.W. Doty c a Université du Québec à Chicoutimi, Chicoutimi, Québec, Canada b Center of Excellence for Research in Engineering Materials (CEREM), College of Engineering, King Saud University, Riyadh, Saudi Arabia c General Motors Powertrain Group, Metal Casting Technology, Inc, Milford, NH, USA article info Article history: Received 13 January 2010 Received in revised form 24 May 2010 Accepted 6 June 2010 Keywords: Machinability Al–Cu alloys Free-cutting elements Drilling Tapping abstract This study was undertaken to investigate the machinability aspects of four new Al–Cu casting alloys with regard to the drilling and tapping processes; the base alloy is the 220 Al–2%Cu–1.3%Si–0.4%Mg alloy from which the other three alloys were prepared through the addition of TiB 2 and Zr, Sn, and Bi. The machining performance was evaluated based on the calculation of the total cutting force and moment together with that of the tool life expressed as the number of holes drilled/tapped up to the point of tool breakage. The evaluation range was limited by a predefined targeted tool life of 2520 holes corresponding to 14 machinability test blocks. The results show that more than 2520 holes can be drilled for all the alloys studied without drill breakage. The addition of Sn and Bi decreases the total drilling force over the evaluation range by 14% and 25%, respectively, compared to the base alloy. The total drilling moment was reduced by almost the same ratios. All the alloys studied produce a fan-shaped chip which is considered to be the ideal chip for most drilling applications. The addition of Bi increases chip fragility considerably whereas no distinct change in chip characteristics was caused by the addition of Sn. No significant drill wear or any outstanding change in the built-up edge (BUE) to be observed with the progress of the drilling process. A comparative study was also carried out on the machining behavior of these new alloys, represented by their base 220 alloy, with that of the A206, 356, B319, and A319 alloys. Results revealed that the 220 alloy may be proposed as a promising cheaper and lighter alternative for the machining application of the A206 alloy. Furthermore, the machinability of the 220 alloy may be deemed an acceptable compromise between that of the 356 and B319 alloys, on the one hand, and that of the A319 alloy on the other. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The term machinability can refer either to the ease or difficulty of machining a material. The most commonly used criteria for assess- ing machinability are the cutting force (or power consumption) and chip form (Barth, 1985; Drozda and Wick, 1983; Cook, 1975). Machinability increases as the cutting force and power consump- tion decrease for the cutting conditions of interest. Lower cutting forces imply lower tool-wear rates, better dimensional accuracy, and increased machine tool life. Based on the chip form crite- rion, materials producing short chips which are easily managed and disposed of are more machinable than those which produce long unbroken chips or small, powder-like chips. Chip form is often used to assess the machinability of soft, ductile alloys, especially aluminum alloys. Chip control is an important issue especially in drilling oper- ations involving ductile work materials such as aluminum alloys. ∗ Corresponding author. Tel.: +1 4185455011; fax: +1 4185455012. E-mail address: fhsamuel@uqac.ca (F.H. Samuel). Chip control usually involves two tasks; that of the breaking of chips to avoid the formation of long continuous chips which can become entangled in the machinery, and that of the removal of chips from the cutting zone to prevent damage to the machined surface. Chip- breaking and removal are of great importance in drilling, since the allowable penetration rate is often limited by chip-breaking char- acteristics. There are two common strategies which may be applied to accomplish chip-breaking. In the first strategy, the cutting tool is fitted with a chip breaker, which curls up the continuous chip into a tight spiral producing a high bending stress sufficient to fracture it (Kaldor et al., 1979). In the second strategy, the chip-breaking is achieved by developing the workpiece material, that is to say, using free-cutting alloys. This is one of the main objectives of the present work and is reviewed below. The development of free-cutting aluminum alloys is the most common metallurgical technique used to improve the machinabil- ity of this type of alloys. The terms free-cutting or free-machining mean that the chips should flow freely from the specimen being cut, and that they should also be short and breakable to prevent fouling of the cutting tool or other operating parts of the machine. Free-cutting aluminum alloys were prepared from standard heat- 0924-0136/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2010.06.006