Mechanical Alloying of Mg-Al Alloy with Addition of Metal Silicides

Abstract

Mg-Al alloy powder was mechanically alloyed (MA) by addition of metal silicides (TiSi₂, CrSi₂ and WSi₂), using a planetary ball mill under an Ar atmosphere. The MA powders were consolidated via vacuum hot pressing and hot extrusion. Solid state reactions in the MA powders and extruded materials were examined by XRD and TEM. Mechanical properties were evaluated by hardness and compression tests. In all alloy systems, in situ formation of Mg₂Si and metal silicides with lower Si content than the added silicides occurred by solid state reaction during MA and subsequent heating processes. All of the as-extruded materials with fine dispersoids and fine matrix grain structures exhibited high hardness and specific proof strength. The as-extruded material of the Mg-Al-TiSi₂ system showed the highest hardness of 141 HV, 0.2% compressive proof stress of 657 MPa and specific proof stress of 337 MPa/(Mg/m³) at room temperature.