Characterization of the solidification behavior, microstructure and mechanical properties of aluminum alloy 6063 with samarium addition

Abstract

The present work investigates the effects of Samarium (Sm) addition on the performance of 6063 Aluminum alloy. The investigation includes aspects related to the solidification behavior, the microstructure and the mechanical properties for the reference alloy in addition to four modified alloys containing 0.1, 0.3, 0.5 and 1.0 wt% Sm. The reactions corresponding to the formation of α-Al, Al13Fe4, α-AlFeSi and Mg2Si are identified through thermal analysis of the reference alloy. The modified alloys experience similar reactions during solidification that, however, occur at slightly different temperatures, implying the modification of the forming phases due to Sm addition. Optical microscopic examination reveals 37 % grain refinement for the modified alloys due to the Sm addition up to 0.5 wt%. Sm addition influences also the Fe-bearing precipitates, causing the formation of granular Al-Sm-Si-Fe-Mg due to the addition of 0.1 wt% Sm. Samarium addition beyond 0.1 wt% induces the formation of Fe-free Al-Sm-Si-Mg intermetallics, having sharp plate-like and zigzag morphology, in addition to Sm-free Al-Fe-Si precipitates. The best mechanical performance, in the T6 condition, is achieved by the (AA6063 + 0.1 wt% Sm) alloy, attaining an increase of 38 % in the hardness and 11 % in the yield strength, in comparison to the unmodified alloy. The significant strengthening of the 0.1 wt% Sm modified alloy in the T6 condition suggests a promoted precipitation of Mg2Si during solidification due to the Sm addition.