The role of preheating–induced precipitates in tailoring the electrical and mechanical properties of deformed Al–0.1 wt% Sc conductors

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This study investigates the effect of hot deformation temperature on the microstructural evolution and aging behavior of an Al–0.1 wt% Sc conductor alloy. For this purpose, uniaxial hot compression tests were conducted over a temperature range of 350–550 °C, followed by isothermal aging at 300 °C for 24 h. The resulting microstructural evolution was characterized by using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM), while hardness and electrical conductivity measurements were used to evaluate the aging response. The stress–strain behavior indicates that Sc addition increases the flow stress by ~10 MPa at deformation temperatures below 500 °C. However, at 550 °C, the peak flow stresses of both alloys converge to nearly identical values, consistent with near-complete Sc dissolution above the solvus temperature. The Al Sc alloy aged at 300 °C shows that hot deformation at 350 °C and 550 °C provides a favorable balance between electrical conductivity and hardness, achieving ~59% IACS and ~ 71 HV, respectively. In contrast, deformation at 450 °C results in a comparable EC (~59% IACS) but yields the lowest hardness (51 HV). TEM analysis reveals that the significantly lower hardness at 450 °C is mainly attributed to the formation of coarse, chain-like Al 3 Sc precipitates during preheating, which are heterogeneously distributed within the microstructure. In contrast, precipitate formation is kinetically limited at 350 °C by the short preheating duration and thermodynamically absent at 550 °C above the Sc solvus, retaining Sc in supersaturated solution and promoting uniform nanoscale L1 2 -Al 3 Sc precipitation during subsequent aging.