Microstructure evolution of the martensite Co(50)Ni(22)Ga(28) magnetic shape memory alloy was investigated by the method of glass fluxing combined with superheating cycling. A maximum bulk undercooling of 220 K is achieved and a mass of sub-grains are introduced by the undercooling. A number of dislocations and large internal stress, due to the undercooling rapid solidification, give rise to the production of subgrains during the recovery process. These sub-grains, as well as martensite variants, are remarkably refined with the increase of undercooling. The recrystallization and growth of sub-grains during the following annealing are also discussed. (C) 2010 Elsevier B.V. All rights reserved.