Precipitation hardening of Mg±12%Ti wt.%) synthetised by physical vapour deposition G. Garc es * , P. P erez, and P. Adeva Department of Physical Metallurgy. National Centre for Metallurgical Research, CENIM, CSIC., Av. Gregorio del Amo 8, 28040 Madrid, Spain Received 3 April 2001; accepted 24 April 2001 Abstract The precipitation hardening in a Mg±12%Ti obtained by physical vapour deposition has been studied during isothermal treatments at 300°C and 350°C. The formation of ®ne coherent precipitates in the magnesium basal plane at 300°C results in a strengthening of the alloy. The growth of the precipitates along the [0 0 0 1] direction provokes the loss of coherence with the matrix and softening of the alloy. Ó 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved. Keywords: Magnesium alloys; Precipitation hardening; Physical vapour deposition Introduction Magnesium alloys are potentially useful as structural materials in the aerospace and automobile industries due to their low density and high speci®c resistance. However, their low corrosion resistance has limited their application. The corrosion resistance of some magnesium alloys can be enhanced by solid solution of some alloying elements using rapid solidi®cation processes [1±4]. However, they have not been ecient in the case of titanium, zirconium, chromium and vanadium since they present a negligible solubility in liquid magnesium, resulting in the formation of second phase particles which act as galvanic pairs. The physical vapour deposition PVD) technique is presented as an alternative non- equilibrium solidi®cation process to achieve novel alloys hitherto impossible to obtain with other methods [5,6]. In the case of magnesium alloys, this technique has been applied successfully in the case of binary Mg±X X  Ti, Zr, V) [7±9] alloys. The results have shown that this process leads to a re®nement of the microstructure and an im- portant extension of the solid solubility limits of the alloying elements. Moreover, some Scripta Materialia 45 2001) 1001±1007 www.elsevier.com/locate/scriptamat * Corresponding author. E-mail address: ggarces@cenim.csic.es G. Garc es). 1359-6462/01/$ - see front matter Ó 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved. PII:S1359-646201)01095-8