Structures and Properties of P/M Materials of Al-Mg-oxide (GeO₂, SnO₂, PbO) Systems Processed by Mechanical Alloying

Abstract

With a purpose of obtaining materials of high specific strength at room and high temperatures, Al-8at%Mg mixed powder was mechanically alloyed with addition of oxide powders (GeO₂, SnO₂, PbO) of the Group IV elements of the periodic table. Solid state reactions during mechanical alloying (MA) and subsequent thermomechanical processing were studied. The MA powders were consolidated to the P/M materials by vacuum hot pressing and hot extrusion, and their solid state reaction and mechanical properties were studied. It was observed by X-ray diffraction that PbO was decomposed during MA, while GeO₂ and SnO₂ were decomposed during hot pressing. Reduced Ge and Sn were combined with Mg to form Mg₂Ge and Mg₂Sn, while reduced Pb remained as metallic Pb. Preferential oxidation of solute Mg occurred resulting in formation of MgO and MgAl₂O₄. The P/M material of Al-Mg-GeO₂ system is harder and more ductile than those of Al-Mg-SnO₂ and Al-Mg-PbO systems. The P/M material of Al-Mg-GeO₂ showed the highest tensile strength of 629 MPa at RT and 361 MPa at 473K.