In situ processing and aging behaviour of an aluminium/Al2O3 composite

Reactive sintering involving a displacement reaction between aluminium and CuO powders was applied to fabricate an aluminium based composite. The two powders were mixed in a ball mill and uniaxially pressed before sintering in nitrogen atmosphere at 900 °C. During sintering a displacement reaction between CuO and aluminium occurred, which resulted in in situ synthesis of alumina particles. Differential thermal analysis (DTA), X-ray diffractometry (XRD), optical and scanning electron microscopies were used to investigate the phase and microstructural changes taking place during processing of the composite. Results revealed that no chemical reaction occurred during ball milling and Al2O3 phase developed in two stages during sintering of the compact. Below 700 °C, amorphous alumina formed which transformed to crystalline alumina at higher temperature. Aging response of the composite was examined as a function of time in temperature range of 180–220 °C. Composite attained a peak hardness value of 133 Hv after 4 h of aging at 200 °C.