THE ROLE OF STRAIN IN THE NUCLEATION OF SOLID STATE TRANSFORMATIONS.
Final rept. for 1 Jun 61-1 Sep 64,
ILLINOIS UNIV URBANA
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The allotropic transformations in iron, cobalt, cerium, and lanthanum were studied with the objective of establishing the factors which are influential in the initiation and propagation of the transformation. From a study of zone-refined iron it was concluded that interstitial solutes are not essential for the martensitic transformation of iron. The FCC-HCP martensitic transformation was studied in whiskers, bulk single crystals and polycrystalline specimens of cobalt. From the measured effect of stress on the transformation it was concluded that the transformation was very defect sensitive and the habit plane was not controlled by a critical resolved shear stress criterion. In cerium, both the FCC-FCC and FCC-HCP transformations were studied in polycrystalline specimens. The FCC-HCP transformation in lanthanum was found to occur isothermally, in contrast to the other allotropic transformations studied in this work. Author