Hypercooling was achieved in both Co80Pd20 alloys and Ni80Pd20 alloys by applying the fluxing method. Microstructures and substructures of the as-solidified hypercooled Co80Pd20 alloys and Ni80Pd20 alloys were investigated. High densities of low-angle grain boundaries, dislocations networks were observed in the as-solidified hypercooled specimens. These substructures suggest a partial recrystallization occurring in the as-solidified specimens. After recrystallization annealing, the coarse grained microstructures of the quenched alloy refined. These results are believed as the evidences of recrystallization mechanism of grain refinement in these highly undercooled single phase alloys. (c) 2013 Elsevier B.V. All rights reserved.