Mechanically Alloyed P/M Composites of Al-Mg-Silicide and Al-Mg-Oxide Systems

Abstract

Al-Mg alloy powder was mechanically alloyed with addition of metal silicide and metal oxide powders. The metal silicide powders of CrSi 2 , TiSi 2 , ZrSi 2 , WSi 2 , MoSi 2 and metal oxide powders of B 2 O 3 , Sc 2 O 3 , TiO 2 , SrO 2 , CeO 2 were added to Al-8at%Mg alloy, and mechanical alloying (MA) treatment was conducted by using an attritor-type ball mill. Solid state reaction during MA and subsequent heating was studied. The MA powders were consolidated to the P/M composites by vacuum hot pressing and hot extrusion, and their structures and mechanical properties were examined. It was shown that all added oxides but TiO 2 were decomposed during heating of the MA powders, and aluminide compounds and spinel (MgAl 2 O 4 ) were formed within the Al-Mg alloy matrix. All added silicides were only partially decomposed and Mg 2 Si was formed during heating of the extruded P/M composites. Structural coarsening during heating of the Al-Mg-silicide system was more pronounced than that in the Al-Mg-oxide system. The P/M composites of Al-Mg-oxide system showed higher hardness than those of the Al-Mg-silicide system. The highest hardness of 237HV was observed for Al-Mg-B 2 O 3 P/M composite. The P/M composite of Al-Mg-CrSi 2 showed the highest tensile strength of 578MPa. Although high tensile strength was obtained, Al-Mg-silicide composites showed poor ductility.