Precipitation behavior of 14H-LPSO structure in Mg–12Gd–2Er–1Zn–0.6Zr Alloy

摘要

The microstructures of as-cast and as-solution Mg–12Gd–2Er–1Zn–0.6Zr alloys were investigated by optical microscopy(OM), scanning electron microscopy(SEM), transmission electron microscopy(TEM), highresolution transmission electron microscopy(HRTEM)X-ray diffraction(XRD) and selected-area electron diffraction(SAED) in the present investigation. The results show that the primary eutectic phase Mg_5(Gd, Er, Zn) and some flocculent features are found in the as-cast alloy; the SAED pattern indicates that these flocculent features are the dense areas of stacking faults. The 14H-LPSO structure precipitates in the temperature range of 673–793 K, and the volume fraction of 14H-LPSO structure increases with the extension of heating time; however, there is no precipitation of 14H-LPSO structure when the temperature reaches up to 803 K. In addition, the Mg_5(Gd, Er, Zn) phase dissolves gradually along with the precipitation of 14H-LPSO structure.