Second phase formation in melt-spun Mg-Ca-Zn alloys

Three ternary alloys based on the Mg-Ca-Zn system were produced by melt spinning in the form of ribbons. The alloys were analyzed by X-Ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) with scanning transmission electron Microscopy (STEM) and scanning electron microscopy (SEM). All the alloys showed a difference in microstructure between the wheel contact side and the free surface side. The second phase found in the three ternary alloys studied was identified as the compound Ca2Mg6Zn3 (trigonal with space group P3-bar1c and lattice parameters a=0.97 nm and c=1.0 nm). The alloys thermal behavior was investigated by measuring the changes in microhardness after isochronal aging and only a modest age hardening behavior was observed principally in one of the alloys. The alloys phase stability was also studied by differential scanning calorimetry (DSC) and the results indicate that the melting onset for the three alloys is near 400 deg.C and it decreases with Zn content