Journal of Alloys and Compounds 425 (2006) 334–338 Supersaturated Cu–Li solid solutions produced by mechanical alloying P.A. Rojas a , A. Pe ˜ naloza a , C.H. W ¨ orner a , R. Fern´ andez b , A. Z ´ u˜ niga c,∗ a Instituto de F´ısica, Pontificia Universidad Cat´ olica de Valpara´ıso, Av. Brasil 2950, 2340000 Valpara´ıso, Chile b Departamento de F´ısica, Universidad Cat´ olica del Norte, Av. Angamos 0610, Antofagasta, Chile c Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616, USA Received 2 December 2005; accepted 13 January 2006 Available online 20 February 2006 Abstract In the present work the effect of milling parameters, such as the ball-to-powder ratio and milling time, on the formation of supersaturated Cu–Li solid solutions produced by mechanical alloying was investigated. The microstructural changes and the phases present after milling were analyzed using scanning electron microscopy and X-ray diffraction, whereas the amount of lithium was measured by atomic absorption spectroscopy. The results show that the solubility limit of Li in Cu can be extended up to a maximum value of 17 at.%. It was also observed that the lattice parameter of the copper matrix and the microhardness of the as-milled powder both changed as a function of the lithium content. © 2006 Elsevier B.V. All rights reserved. Keywords: Metals and alloys; Nanostructured materials; Powder metallurgy; Mechanical alloying; X-ray diffraction 1. Introduction With a density of only 535 kg/m 3 (a third of that of magne- sium and less than a fifth of that of aluminum), lithium is the lightest metal. Lithium also possesses several properties that are useful for lightweight applications. For instance, it is known that lithium additions into aluminum have beneficial effects, such as reduced density, and increased stiffness (Young’s modulus) [1]. Besides these low-Z number alloys, the effect of lithium has also been investigated in high-Z number alloys. In this regard, little over 20 years ago, the use of copper–lithium alloys as material to coat the surfaces of structural components in fusion devices was proposed [2–4]. The low-Z number of lithium is the key property in these applications because it helps reducing the con- tamination by erosion [5–10]. In the last few years several efforts have been made in order to produce Cu–Li alloys via process- ing techniques that do not involve fusion. This is so because fusion requires extremely complex processing steps that arise from the differences in fusion and boiling temperatures between copper and lithium. Following this line, Pe˜ naloza et al. [11–16] have successfully obtained Cu–Li alloys by electrodeposition. According to their reports, it has been possible to produce alloys ∗ Corresponding author. E-mail address: apzuniga@ucdavis.edu (A. Z´ u˜ niga). with an atomic content of lithium (at room temperature) close to the maximum solubility of Li in Cu. In the present study, the alternative of producing Cu–Li alloys by mechanical alloying has been explored; and one of the key advantages that mechan- ical alloying has over fusion is that all the reactions occur in the solid state [17–20]. A survey of the literature [17–23] reveals that there are no systematic studies on the response of the Cu–Li sys- tem upon high-energy milling. However, it has been reported that elements with limited solubility in copper such as Ag, Co, Fe and Nb can be successfully alloyed with copper using mechanical milling, and with the extra benefit of a much broader solubility range when compared to the same alloys produced by conven- tional methods [24]. The possibility of incorporating a large amount of lithium in solid solution in copper might result in a series of changes in properties that have not yet been evaluated. This work represents the starting point of a research effort to optimize the milling parameters in the Cu–Li system in order to incorporate as much lithium in solid solution as possible. 2. Experimental procedure The mechanical alloying was performed in a SPEX 8000D mill, using stain- less steel containers and balls (5 mm in diameter), under an argon atmosphere. The Cu–Li alloy powders were produced by milling 5.85 g of copper powder (99.7% pure, <65 m) and 0.15 g of lithium filing (>99% pure), both purchased from Merck ® . No control agent was employed during milling. After milling, the powders were removed from the containers inside an Ar-filled glove box, 0925-8388/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2006.01.032