A theoretical investigation of orientation relationships and transformation strains in steels

Koumatos, K and Muehlemann, A (2017) A theoretical investigation of orientation relationships and transformation strains in steels. Acta Crystallographica Section A: Foundations and Advances, A73. pp. 115-123. ISSN 2053-2733

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Abstract

The identification of orientation relationships (ORs) plays a crucial role in the understanding of solid phase transformations. In steels, the most common models of ORs are the ones by Nishiyama–Wassermann (NW) and Kurdjumov– Sachs (KS). The defining feature of these and other OR models is the matching of directions and planes in the parent face-centred cubic gamma phase to ones in the product body-centred cubic/tetragonal alpha\alpha' phase. In this article a novel method that identifies transformation strains with ORs is introduced and used to develop a new strain-based approach to phase-transformation models in steels. Using this approach, it is shown that the transformation strains that leave a close-packed plane in the gamma phase and a close-packed direction within that plane unrotated are precisely those giving rise to the NW and KS ORs when a cubic product phase is considered. Further, it is outlined how, by choosing different pairs of unrotated planes and directions, other common ORs such as the ones by Pitsch and Greninger–Troiano can be derived. One of the advantages of our approach is that it leads to a natural generalization of the NW, KS and other ORs for different ratios of tetragonality r of the product body-centred tetragonal alpha' phase. These generalized ORs predict a sharpening of the transformation textures with increasing tetragonality and are thus in qualitative agreement with experiments on steels with varying alloy concentration

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Mathematics
Research Centres and Groups: Analysis and Partial Differential Equations Research Group
Subjects: Q Science > QA Mathematics
Q Science > QC Physics > QC0120 Descriptive and experimental mechanics
Depositing User: Konstantinos Koumatos
Date Deposited: 02 Mar 2017 09:33
Last Modified: 06 Mar 2017 16:29
URI: http://sro.sussex.ac.uk/id/eprint/66965

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