Microstructure evolution of the undercooled Co-Ni-Ga magnetic shape memory alloy

▶ The martensite variants are refined with the increase of undercooling. ▶ A mass of sub-grains are induced by undercooling rapid solidification. ▶ The production of sub-grains is attributed to the rearrangement of dislocations. ▶ The sub-grains can recrystallize and grow up during the following annealing.