Effects of high energy grinding under different atmospheres on the solubility of lithium in copper an pure copper

The mechanical alloying process (MA) has successfully obtained supersaturated solid solutions in a great many binary systems. Increased solubility of over 90% compared to the maximum in equilibrium for the solutes Ag and Co and increases greater than 50% for Cr and Fe have been reported after using MA for the production of copper-based alloys. This has led to the development of much research to determine the maximum solubilities in solid state that can be reached with this process and for different solutes. Lithium is one of the elements investigated. Unlike other metallic elements, lithium has had, comparatively speaking, a recent introduction in the area of investigation of structural materials. The reason is simple, none of lithium's properties had been fundamental in this field until a little more than three decades ago. Lithium is an element with exceptional chemical and physical properties but due to its high reactivity, obtaining it complicates the operating conditions under which it is processed. The formation of a copper-based alloy with lithium has major theoretical advantages particularly relative to reducing the density of the copper-based alloy. However, these elements have other physical and chemical properties that complicate this development when using conventional alloying production processes, particularly those involving a fusion stage, so the use of mechanical alloying as an alternative process has been proposed. Besides developing in solid state, MA has proven to be particularly efficient in obtaining solid solutions of elements that, under conditions of equilibrium, show very limited or even no solubility. This work has studied the effects of two control atmospheres on the high energy grinding of Cu and Li and pure copper, as well as the effect of milling time for both atmospheres. The milling for this study was carried out in a SPEX 8000D mill using a balls to powder ratio of 10:1, with steel containers and balls. The milling times varied from 3 to 30 hours and the control atmospheres used were argon and nitrogen. The microstructural changes of the powders as a function of the variables studied, were analyzed with scanning electron microscopy on a Philips XL-30 SFEG. The phases present in the samples were analyzed using X-ray diffraction on a Siemens 5000 diffractometer. The iron quantities in the samples after milling, were determined with atomic adsorption spectroscopy in a GBS 905 spectrometer and the oxygen contents were determined with infrared spectroscopy on a LECO TC-436 DR. Results show a marked effect of the control atmosphere on the microstructural characteristics and chemical composition of the copper and on the chemical composition in the case of the Cu-Li alloys (cw)