Using ball-indentation to evaluate the properties of an ultrafine-grained Al–2% Si alloy processed by ECAP

As-cast Al–Si alloys exhibit excellent mechanical properties but these properties may be further improved through processing by equal-channel angular pressing (ECAP). In this investigation, specimens of a hypo-eutectic Al–2% Si alloy were successfully pressed up to a maximum of four passes at room temperature and the microstructures and mechanical properties were evaluated. The results show that pressing through four passes reduces the grain size from 40 to 0.70 μm, reduces the size of the Si particles from 12.0 to 1.08 μm and increases the yield stress and the ultimate tensile strength by a factor of 2 by comparison with the as-cast alloy. The mechanical properties were examined using a ball-indentation technique (BIT). It is suggested that, since BIT provides the capability of obtaining extensive mechanical data using only a very small sample, it is an ideal technique for evaluating the properties of samples processed by ECAP.