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.