The internal structure in massive phases formed during six massive transformations has been reviewed. A counterpart review has also been made for the proeutectoid ferrite reaction, mainly in alloy steels in which bulk partition of alloying elements between austenite and ferrite has not occurred. Both dislocations and twins comprise this structure unless the stacking fault energy is too high to permit twin formation. Volume and shape changes associated with transformation can explain dislocation loops through stress-induced displacement and multiplication of misfit dislocations into the softer phase by means of either a dissociation reaction followed by Ashby-Johnson prismatic looping or emanation of glide loops from Frank-Reed sources. Following Gleiter et al., the "growth accidents" concept used to explain dislocation and twin formation during grain growth proves equally suitable for explaining formation of the same features during the massive and other diffusional transformations. Climb of interfaces produced by edge-to-edge rather than the usual plane-to-plane matching, introduced by Kelly and Zhang and experimentally supported by Nie and Muddle and by Howe et al. for the alpha --> gamma transformation in near-TiAl alloys, is proposed as another source of dislocations in the product phase.
|Number of pages||5|
|Journal||Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science|
|Publication status||Published - 1 Aug 2002|