Optimization scheme of the orientation relationship from crystallographic statistics of variants and its application to lath martensite

Abstract Without sacrificing any solution accuracy, an efficient optimization scheme of determining the orientation relationship only based on the daughter phase (i.e., lath martensite in steels in this paper) was established in this work, which involves two key steps. Firstly, an accurate clustering algorithm was developed to perform a statistic of all variants, which can give the most probable orientation and area fraction for each variant. Different from previous methods, the second step is to perform a newly-established optimization scheme, which is able to take variant fractions into consideration to determine the optimal orientation relationship and orientation of prior austenite simultaneously. In this case, the variant-level calculation, which can save much computational time compared with pixel/domain-level calculation, is beneficial for the efficiency promotion. Through inputting the equally-weighted variants into the optimization scheme, the influence of the random cross-sections on the solutions can be effectively eliminated. Furthermore, in-situ high temperature EBSD examinations were first performed to validate solution accuracy, the corresponding results clearly indicated that the orientation of austenite obtained from this approach exhibited a high accuracy and the error is less than 1°.