Effect of A Scandium Addition On An Al-2% Si Alloy Processed by ECAP

Two alloys, Al-2% Si and Al-2% Si-0.25% Sc, were subjected to equal-channel angular pressing (ECAP) up to a maximum of 4 passes using route B-c at room temperature. This processing gave ultrafine-grained microstructures with grain sizes of similar to 0.70 mu m without Sc and similar to 0.30 mu m with the 0.25% Sc addition. The improvement in the mechanical properties of the Al-2% Si alloy due to the Sc addition was studied using a ball-indentation technique (BIT). These tests showed that the addition of 0.25% Sc decreased the grain size of the Al-2% Si alloy in the cast condition from 40 to 25 mu m with an increase in the ultimate tensile strength (UTS) from similar to 106 to similar to 185 MPa. In addition, ECAP of the Al-2% Si-0.25% Sc alloy gave a UTS of similar to 355 MPa which was similar to 30% higher than the Al-2% Si alloy without the Sc addition. This increase is due to the presence of fine Al3Sc precipitates.