Microstructure and mechanical properties of Al-4·5 wt-%Cu/15 wt-%SiC composite prepared using ball mill

Abstract

Aluminium based metal matrix composite (MMC) material was prepared using ball milling (BM). Elemental powders of aluminium and copper, and SiC particle reinforcement were milled in a horizontal ball mill. Two different speeds of rotation of 63 and 113 rev min -1 were employed to investigate the influence of collision pressure. It was observed that SiC particles began to be incorporated into the metal matrix (Al-Cu) after 3·6 ks of BM. After 36 ks of BM, almost no individual SiC particles could be observed. Energy dispersive X-ray analysis showed that copper and SiC particles had already been well distributed in the powder particles after 54 ks. However, aluminium and copper could not be mechanically alloyed, even after 360 ks of BM. Because the BM process was carried out in a low energy ball mill, the size of the SiC particle remained unchanged. Irregularly shaped SiC particles were, however, seen to have been reshaped into a more spherical form thus reducing the stress concentration near the particles. Microstructural observation revealed that the advantage of using a low energy ball mill to produce composite powder particles was that it provided well distributed SiC particles and good bonding between the metal matrix and the SiC particles. The effects of the BM duration and the addition of aluminium on the fracture toughness of the MMC have also been evaluated in the present study. © 1997 The Institute of Materials.