STRUCTURES AND PROPERTIES OF MECHANICALLY ALLOYED ALUMINUM-METAL OXIDE POWDERS AND THEIR P/M MATERIALS

Powders of metal oxides of different standard free energies of formation, CuO, Fe2O3, SiO2 and MgO, were mechanically alloyed with pure aluminum powder by a high energy ball mill under an argon atmosphere. P/M materials were fabricated from mechanically alloyed powders by cold pressing, vacuum degassing and hot extrusion. The solid state reaction of aluminum-oxide systems was studied by DSC analysis and X-ray diffraction. Thermit reaction occurs in Al-CuO and Al-Fe2O3 systems during mechanical alloying and hot extrusion, respectively. In the case of SiO2 and MgO which have a relatively high standard free energy of formation, no reaction with aluminum occurs even after heating of P/M materials at 873 K for 24 h. It is shown by X-ray diffraction and DSC analysis that the Al-CuO system P/M material consists essentially of the Al-Cu alloy matrix with dispersion of Al2O3. The hardness increase by age hardening for Al-CuO P/M material after solutionizing and water-quenching is about half as much as that of I/M Al-Cu alloys. The P/M.material of the Al-CuO system shows the highest tensile strength of 600 MPa at room temperature, whereas that of the Al-Fe2O3 system has the highest tensile strength of 330 MPa at 573 K.