Effect of laser surface remelting on the microstructure and properties of Al-Al2Cu- Si ternary eutectic alloy

Bimodal ultrafine eutectic composites (BUECs) exhibit a good combination of strength and plasticity owing to a dual-hierarchy in eutectic length-scales in the microstructure. The present study investigates the variation of phase, morphology, feature length-scales and modality of microstructures obtained in a Al81Cu13Si6 (at. %) ternary alloy after laser surface remelting. A novel approach of varying component bimodal eutectic volume fractions by controlling the cooling rate of the laser solidification process has been presented. The volume fraction of the fine eutectic matrix has a profound effect on the flow strength. Laser remelted microstructures with volume fractions of the fine eutectic varying from 25 to 40% exhibiting compressive flow strengths ranging from 500 to 900 MPa have been obtained. The volume fraction of the fine eutectic decreased with cooling rate and completely ceased to exist at cooling rates greater than 4 x 10(4) degrees C/ s.