Development of Very High Strength and Ductile Dilute Magnesium Alloys by Dispersion of Quasicrystal Phase

Very high strengths, with tensile yield strength from 377 to 405 MPa, combined with elongation to failure of over 12 pct, have been achieved in Mg-Zn-Y dilute alloys by direct extrusion. Alloys Mg-6xZn-xY, where x = 0.2, 0.35, and 0.5 (at. pct) were chill cast in a steel mold and direct extruded at a temperature in the range 508 K to 528 K (235 A degrees C to 255 A degrees C), which produced an average grain size of about 1 mu m. Quasicrystalline i-phase particles were dispersed in the matrix with size ranging from 50 nm to 1 mu m. In addition, high density of nano-precipitates of average size 15 nm was dispersed in matrix. Thus we have developed magnesium alloys of very high strength combined with ductility by a simple process using extrusion with very little addition of yttrium. (C) The Minerals, Metals & Materials Society and ASM International 2013