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Fractality and reversibility of ferrous martensite
Author(s) -
Hornbogen Erhard,
Skrotzki Birgit
Publication year - 1992
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.199200532
Subject(s) - martensite , austenite , shape memory alloy , bainite , materials science , diffusionless transformation , thermodynamics , metallurgy , shear (geology) , ferrous , microstructure , crystallography , chemistry , composite material , physics
Martensite formation is characterized by a diffusionless structural phase transformation from austenite to martensite, associated with a considerable amount of lattice variant shear γ γα ≍ 0.2. Ferrous martensite shows all possible features connected with the transformation. Different modes of initiation of the martensite formation are possible. The reasons for the burst phenomenon can be considered as an analogy to discontinuous yielding. The transformation only procedes if further thermodynamical driving force is provided by cooling or shear stress. In some cases fractal microstructures are formed in which several fragmentations can be recognized. In contrast to shape memory alloys, steels usually do not show reversibility of the reverse α → γ transformation. The factors which favour reversibility have been defined. Knowledge of these is necessary for the development of iron‐base shape‐memory alloys.