INFLUENCE OF THE CONSOLIDATION STEP ON THE MECHANICAL-PROPERTIES OF RAPIDLY SOLIDIFIED MG-AL-ZN ALLOYS

Mg-15Al-3Zn and Mg-20Al-1Zn (at%) alloys have been rapidly solidified through centrifugal atomization. During the consolidation step of the powder by extrusion, dynamic recrystallization took place in the die, reading to very fine grain sizes ranging from similar to 0.2 to 1 mu m , increasing with ram speed and extrusion temperature. The high yield stress (up to 500 MPa) so obtained mainly results from the grain bound ary contribution to hardening. Since, experimentally, the finer the in itial microstructure, the finer the grain size in the as-consolidated state, the choice of the RS route appears valuable. In addition, law r am speed and extrusion temperature are needed to ensure the smallest p ossible grain size and to limit second phase coarsening, while a high enough content of allaying element is required in order to avoid grain growth during dynamic recrystallization, but limited to similar to 15 at% in order to maintain some ductility.