Abstract
Transformation characteristics of iron precipitates formed in a Cu-2 wt.-%Fe alloy aged at 800°C have been investigated by means of high-voltage electron microscopy, especially by utilizing the selected micro area electron-diffraction technique which makes it possible to take diffraction patterns from within a single precipitate. In the iron precipitates a banded structure is observed with alternate light and dark contrasts, and is unambiguously verified to consist of alternate lamellae of two bee martensite regions which are twin-related to each other with respect to a (112) plane. It is thus clearly shown that the iron precipitates completely undergo martensitic transformation, even when they are embedded in an inert matrix. Thinning of specimenscan also promote martensitic transformation as well as deformation and the extraction of precipitates from specimens. The orientation relationship between the martensite (α′) and surrounding matrix (E) crystals is determined to be (111)ɛ|(011)α′, [101]ɛ‖[111]α′; this is the Kurdjumov-Sachs orientation relationship, inagreement with previous work by Easterling and Weatherly.
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