The crystal structure and thermal stability of intermetallic particles in the as-cast microstructures of a Mg-8Zn-4Al-0.5Ca (wt ) casting alloy have been characterized using transmission electron microscopy and electron diffraction. It is found that these particles have an average composition of Mg6Zn9Al4Ca and a primitive cubic structure, with space group Pm(3) over bar n and a lattice parameter of 1.43 +/- 0.18 nm. The proposed structure is distinctly different from that of the equilibrium T phase (Mg-32(Al,Zn)(49)), which is often reported to form in alloys of similar compositions. These primary intermetallic particles are thermally stable at temperatures close to the melting point of the alloy. They are still detectable in samples subjected to isothermal heat treatments at 325 degrees C for up to 720 h.
|Pages (from-to)||755 - 762|
|Number of pages||8|
|Journal||Philosophical Magazine Letters|
|Publication status||Published - 2006|