A theoretical investigation of orientation relationships and transformation strains in steels

作者：Koumatos K^*; Muehlemann A

来源：Acta Crystallographica A-Foundation and Advances, 2017, 73(2): 115-123.

DOI：10.1107/S2053273316020350

• orientation relationships
• Nishiyama-Wassermann
• Kurdjumov-Sachs
• Pitsch
• Greninger-Troiano
• Bain
• inverse Greninger-Troiano
• steel
• ratio of tetragonality
• transformation strains
• f.c.c. to b.c.c. transformations
• f.c.c. to b.c.t. transformations

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.

• 出版日期2017-3