A diffusionless transformation is a phase change that occurs without the long-range diffusion of atoms but rather by some form of cooperative, homogeneous movement of many atoms that results in a change in crystal structure. These movements are small, usually less than the interatomic distances, and the atoms maintain their relative relationships. The ordered movement of large numbers of atoms lead some to refer to these as military transformations in contrast to civilian diffusion-based phase changes.
The most commonly encountered transformation of this type is the martensitic transformation which, while being the most studied, is only one subset of non-diffusional transformations. The martensitic transformation in steel represents the most economically significant example of this category of phase transformations but an increasing number of alternatives, such as shape memory alloys, are becoming more important as well.
Other articles related to "diffusionless transformation, transformation":
... In addition to displacive transformation and diffusive transformation, a new phase transformation that involves displasive sublattice transition and atomic ... The new transformation mechanism has been christened a pseudomartensitic transformation ...