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.