Effect of Al–5Ti–1B–La intermediate alloy on microstructure and mechanical properties of A356.2 aluminum alloy

This study delves into the effects of Al–5Ti–1B–1La intermediate alloy, a newly developed refinement agent, on the microstructure and mechanical properties of A356.2 aluminum-silicon alloy modified by Al–10Sr. The decomposition of Ti₂Al₂₀La, where La element was concentrated in the Al–5Ti–1B–1La intermediate alloy, hardly affected the conventional nucleation mechanism of TiAl₃–TiB₂; nonetheless, the La element significantly refined the dendritic arms of α-Al. Notably, the secondary dendrite arm spacing was reduced from 49 μm to 27 μm, when 0.025 wt% ∼0.2 wt% Al–5Ti–1B–1La intermediate alloy and 0.014 wt% Al–10Sr modifier was incorporated to the A356.2 aluminum alloy. Although the room-temperature ultimate tensile strength was increased only by 30 MPa, the elongation was remarkably improved from 10% to 26%. The hardness of the alloy was also enhanced from 75 HBW to 84 HBW. The experimental outcomes underscore the efficacy of minimal La element incorporation in enhancing the performance of Al–5Ti–1B intermediate alloy, and the findings are significant for improving the serviceability of automobile wheels made from A356.2 aluminum alloy. The method used in this study can also be employed to regulate the microstructure and enhance mechanical properties of other sub-eutectic aluminum-silicon alloys.