The phenomenon in which atoms or groups of atoms coordinate to displace their neighboring counterparts resulting in structural modification is known as a displacive transformation. The scope of displacive transformations is extensive, encompassing a diverse array of structural changes. As a result, additional classifications have been devised to provide a more nuanced understanding of these transformations. Austenite exhibits a
face-centered cubic (FCC) unit cell, whereas the transformation to martensite entails a distortion of this cube into a
body-centered tetragonal shape (BCT). This transformation occurs due to a displacive process, where interstitial carbon atoms lack the time to diffuse out. Consequently, the unit cell undergoes a slight elongation in one dimension and contraction in the other two. Despite differences in the symmetry of the crystal structures, the chemical bonding between them remains similar. The iron-carbon martensitic transformation generates an increase in hardness. The martensitic phase of the steel is supersaturated in carbon and thus undergoes
solid solution strengthening. Similar to
work-hardened steels, defects prevent atoms from sliding past one another in an organized fashion, causing the material to become harder. ==Pseudo martensitic transformation==