Direct Analysis of Twinning in Low Alloy Martensite

H. K. D. H. Bhadeshia and D. V. Edmonds
University of Cambridge


The deformation processes involved in the formation of low alloy martensites appear from microstructural observations to be essentially slip. This is deduced from observations of dislocation density. However, twins are occasionally found. To examine whether these are transformation or accommodation twins, a novel method has been used to retain austenite, thus enabling a direct crystallographic study.

For a lattice-invariant deformation, the theory of martensite requires that the twin plane should correspond to a plane of mirror symmetry in the austenite. The measurements show that this is not consistently the case, indicating that the observed twins are really acommodation defects.

Phase Transformations, York Conference, April 1979 The Institution of Metallurgists, Series 3, No. 11, Vol. 2, pp. IV-4 to IV-8

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