한국주조공학회

Al-Cr alloy with composition in the range from 1.5 wt% to 10 wt% Cr were rapidly solidified from the melt by the single roller method. The supersaturated solid solution was obtained up to 6 wt% Cr in Al-Cr alloy for 20μм thickness. Lattice parameter decreased with increasing Cr content at the rate of 0.00456A per wt% Cr up to 6 wt% Cr. Microhardness increased with increasing Cr content at the rate of 10Kg/mm^2 per wt% Cr up to 6 wt% Cr. Microhardness measurements on the Al-6 wt% Cr supersaturated solid solution annealed isothermally showed no sign of age hardening. Decomposition temperature, determined by lattice parameter changes and microhardness changes, was 470℃ for Al-6 wt% Cr supersaturated solid solution. Transmission electron microscopy showed that decomposition within one hour below 400℃ occurred at grain boundaries only, and also the additional decomposition within grains being evident at 450℃ The coarse precipitate structure showed at 500℃ and 550℃, respectively. The coarse precipitate structure is considered Al_7Cr.