Effect of different Co contents on the microstructure and tensile strength of Mg-Co-Y alloys

As-cast and as-extruded Mg-x at% Co-6 at% Y (x = 0, 1, 2, 4) alloys were prepared. Their tensile strengths and microstructures were examined by using a WDW-200E material testing machine, X-ray diffractometer (XRD), optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The tensile strength of the as-cast Mg-x at% Co-6 at% Y (x = 0, 1, 2, 4) alloys reached the peak value of ~246 MPa with the addition of 1 at% Co. Additionally, the tensile strength of the as-extruded Mg-x at% Co-6 at% Y (x = 0, 1, 2, 4) alloys reached the peak value of ~369 MPa with the addition of 1 at% Co. The long-period stacking-ordered (LPSO) phase played a highly important role in the strengthening mechanism of the as-cast and as-extruded Mg-x at% Co-6 at% Y (x = 0, 1, 2, 4) alloys.