A Variant Selection Model for the Prediction of Fcc-To-Bcc Transformation Textures

C S Da Costa Viana,J J Jonas,M P Butron-Guillen

doi:10.1155/tsm.26-27.599

Abstract

In the present work, a simple model is described for the prediction of fcc-to-bcc transformation textures. It employs a discrete distribution of orientations and is based on the Kurdjumov-Sachs relationship for the γ -to- α transformation. An important feature of the model involves the variant selection rule, which assumes that nucleation is favoured according to a slip system based variant selection criterion. Subsequent selective growth involves a transformation work rule based on the Bain strains and the presence of an internal stress field. The transformation texture predicted from an experimental 95% cold rolled Ni-30wt%Co alloy texture is compared to experimental martensite textures for both a Nb-microalloyed steel and a Fe-30%Ni alloy. The predicted texture displays better agreement with the steel data.

Highlights

The inheritance of preferred orientations during the 7-to-a transformation has been under investigation for a considerable time
Evidence has been presented for the validity of the Nishiyama-Wassermann (Nishiyama, 1936; Wassermann, 1933) relationship, with variant selection, with regard to the transformation of a deformed, cube textured, Fe-30%Ni alloy (Liu and Bunge, 1991)
A slip system based variant selection assumption was used as a nucleation rule, which eliminated some of the 24 possible product nuclei that satisfy the K-S relationship

Summary

Introduction

The inheritance of preferred orientations during the 7-to-a transformation has been under investigation for a considerable time. Comprehensive reviews of transformation textures have been published recently (Inagaki, 1981; Yutori and Ogawa, 1981; Ray and Jonas, 1990; Ray et al, 1994) coveting broad aspects of this topic. These surveys have shown that the formation of ferrite, martensite and bainite follows the general predictions of the Kurdjumov-Sachs (K-S) orientation relationship (Kurdjumov and Sachs, 1930), frequently only a resticted set of the 24 possible K-S variants is formed during the transformation (King and Bell, 1975; Davies and Bateman, 1981; Honeycombe, 1981). These authors were able to establish a connection between the selected transformation variants and certain austenite slip directions that were active during the previous rolling deformation

Methods

Results

Discussion

Conclusion