Tensile deformation and heating experiments were performed in a high-voltage electron microscope in order to clarify the mechanism controlling partial dislocation motion in a Fe-Mn-Si shape-memory alloy. It was found that a low-angle boundary composed of three types of perfect dislocation acted as a dislocation source via a pole mechanism. A dislocation reaction which generated a pole dislocation was found to be:

(a/2)[1¯10] + (a/2)[011] + (a/2)[0¯11]  (2a/3)[1¯11] + (a/6)[¯112]

 
where the first term in the right-hand side was the pole dislocation proposed by Seeger. Another aspect of the present study concerned the ε→γ reverse transformation governed by partial dislocation motion upon heating. It was shown that the reverse transformation temperature depended strongly up the structure of ε-martensites interacting with other ε-martensites. The simpler martensites reverse transformed at a lower temperature. It was also demonstrated that small α-martensites were formed at the intersection of two ε-martensites under certain experimental conditions and that they reverse transformed at 773K.

In situ Observation of Partial Dislocation Motion during γ→ε Transformation in a Fe-Mn-Si Shape Memory Alloy. Y.Hoshino, S.Nakamura, N.Ishikawa, Y.Yamaji, S.Matsumoto, Y.Tanaka, A.Sato: Materials Transactions, 1992, 33[3], 253-62