The microstructure of metastable magnesium-titanium alloys grown by vapour deposition

The microstructure of metastable magnesium-titanium alloys grown by physical vapour deposition (PVD) have been evaluated by the use of both scanning and transmission electron microscopy and associated analytical techniques. A combination of high resolution electron microscopy (HREM), electron energy loss spectroscopy (EELS), energy dispersive X-ray analysis (EDX) and standard electron diffraction were used to obtain direct confirmation that up to 32wt% Ti can be retained in solid solution with Mg using PVD. The breakdown temperature of this solid solution occurs between 200 degrees C and 270 degrees C depending on its concentration. This breakdown was attributed to growth within the close-packed layers of planar Ti epitaxial with the Mg matrix. Subsequent growth of the precipitates along the c-axis produced a generally homogeneous distribution of pure Ti precipitates.