Role of homogenization on tensile properties and microstructures in a dilute Mg-Zn-Ca-Mn alloy sheet

The effect of homogenization on microstructures and tensile properties in a dilute Mg-Zn-Ca-Mn alloy sheet was investigated. High-temperature homogenization at 480 degrees C dissolved eutectic intermetallic phases before rolling; however, there was a significant growth of alpha Mn precipitates, resulting in a coarse grain structure in the rolled and annealed alloy sheet. Although rolling without homogenization or after low-temperature homogenization led to a slight increase in the fraction of intermetallic phases in the annealed state, fine grain structure was achieved due to finely dispersed alpha Mn precipitates. Especially, fine average grain size of 8.9 mu m was obtained without any homogenization, and the annealed sheet exhibited good 0.2% tensile yield strength and elongation to failure of 176 MPa and 23.4% along the rolling direction. Unfortunately, the annealed sheet had an in-plane yield anisotropy, but the moderate 0.2% tensile yield strength of 142 MPa could be kept even along the transverse direction due to its fine grain structure.