Phase evolution and thermal stability of 2 Mg–Cu alloys processed by mechanical alloying

• Study of phase evolution of elemental powders Mg and Cu by mechanical alloying.
• The presence of an amorphous precursor which crystallizes to Mg2Cu can be observed.
• Establishing the sequence of phase transformations leading to the formation of Mg2Cu.
• The feasibility to obtain Mg2Cu by means two possible routes has been established.

Phase evolution during mechanical alloying (MA) of elemental Mg and Cu powders and their subsequent heat treatment is studied. Elemental Mg and Cu powders in a 2:1 atomic ratio were mechanically alloyed in a SPEX 8000D mill using a 10:1 ball-to-powder ratio. X-ray diffraction (XRD) shows that the formation of the intermetallic Mg2Cu takes place between 3 and 4 h of milling, although traces of elemental Cu are still present after 10 h of milling. The thermal behavior of different powder mixtures was evaluated by differential scanning calorimetry (DSC). The combination of DSC, heat treatment and XRD has shown a sequence of phase transformations that results in the intermetallic Mg2Cu from an amorphous precursor. This amorphous phase is converted into Mg2Cu by heating at low temperature (407 K). Short MA times and the formation of the amorphous precursor, together with its subsequent transformation into Mg2Cu at low temperatures; represent an advantageous alternative route for its preparation.