Achieving Yield Symmetry in an Extruded Mg-Zn-Y Alloy by More Effective Dispersion of Quasicrystalline i-Phase

A better dispersion of quasicrystalline icosahedral i-phase is achieved in a Mg-3 at. pct Zn-0.5 at. pct Y (ZW82) alloy by a process involving two direct extrusions here. It is confirmed by particle size and distribution analysis that the finer distribution of the particles results from breakage and refinement of the larger particles within the matrix. Better particle distribution resulted in full recrystallization, reported in this alloy composition for the first time. Consequently, a tension-compression yield symmetry was achieved even with a relatively large grain size of about 5 μm. A weaker basal texture (maximum intensity 5.283) played an important role in the strengthening. Yield strengths of about 259 MPa in tension and 269 MPa in compression, with large tensile elongation of 28 pct and compressive elongation of about 20 pct, were obtained. Thus, full recrystallization assisted by finer dispersion of icosahedral phase strengthens the alloy against twinning to remove yield asymmetry, even in a relatively larger grain size alloy.