The effect of Zr addition on the grain refinement of commercial pure aluminium (99.7%) has been investigated in the present study. The results showed that addition of up to 0.3wt. % Zr significantly decreases the average grain size of aluminium from 1100 µm to 162 µm at holding time of 90 seconds. The refining effect of zirconium is attributed to the presence of Al 3 Zr particles in Al-Zr master alloy. These particles are acting as effective heterogeneous nucleating sites for α-Al.

The effect of joint addition of Zr, Ti and Cr on the grain refinement of commercial pure aluminium (99.7% Al) has been investigated by optical microscopy and scanning electron microscopy (SEM) as well as Energy Dispersive X-ray Spectroscopy (EDS). It was found that joint addition of 0.15 wt% Zr and 0.025 wt% Ti to Al can result in a remarkable refinement with an average grain size of 102 μm. It was found the optimum addition level of Ti to be 0.025 wt% in the presence of 0.1 % Zr and any increase in the Ti beyond 0.025wt% results in coarse grain size. Joint additions of 0.15 wt% Zr, 0.025 wt% Ti and 0.15 wt% Cr to Al facilitate better grain refinement and the average grain size was 75 μm. The grain refining performance of joint addition of 0.1 wt.% Zr and different additions of either Ti or Cr is higher than refining with zirconium alone. EDS and SEM analysis of the precipitated phases observed at or near the centers of the refined aluminium with joint addition of Zr and Ti was found to be Al3(Zr1-xTix). These Al3(Zr1-xTix) particles act as heterogeneous nucleation sites for α-Al during solidification and resulted in better grain refinement.