A deformed ultra fine grain is comprised of a spherical body and a tail-like projection projecting from the surface of the spherical body. The tail-like projection exhibits a separating effect on the adjacent deformed ultra fine grains and therefore, aggregation of the ultra fine grains is avoided. Bulk quantities of the deformed ultra fine grains are produced by evaporating a metal by a plasma arc in a controlled atmosphere having a gas that combines with the material of the spherical body to form the tail-like projection.