Amorphization and precipitation within the amorphous layer induced by dry sliding wear of an Al-Si/SiCp composite material

Amorphization and precipitation have been observed within a surface mixed layer which was formed by unlubricated reciprocal sliding wear on the surface of Al-Si/SiCp composite. By using transmission electron microscopy, the characterizations of the amorphous phase and the crystal precipitates have been carried out. It has been identified that the precipitates possess tetragonal symmetry, and the lattice parameters of the precipitates have been determined. Internal twinning was also observed in the precipitate particles. EDS analysis indicates that the chemical composition of the precipitates was different from the amorphous phase. The results show that the precipitates might be produced in conjunction with the formation of the amorphous phase during the sliding wear. The formation mechansims of the amorphous phase and the precipitates have been discussed in detail in terms of defects (i.e. dislocations and substructures) and thermodynamic changes induced by the unlubricated wear. Copyright (C) 1996 Acta Metallurgica Inc.