The coexistence of the martensite matrix and
untransformed a-ferrite particles can also be evidence
of the occurrence of such a transformation. The disappearance
of these a-ferrite particles during annealing
(not shown here) also proves that these particles are
the untransformed product in the solid-state d ! c
transformation. On this basis, it can be concluded that
the solid-state d ! c transformation does indeed exist
when DT > DT* and the d phase always forms as the
primary phase independent of DT.