Exploring the origin of variant selection through martensite-austenite reconstruction

Texture evolution during processing and post-processing of maraging steel fabricated by laser powder bed fusion

“…The phenomenological theory of austenite–martensite dictates that there is an equal proability of the formation of all 24 variants in the absence of variant selection. Though V4 and V8 appear to have a higher frequency, the average variant selection index (VSI), as proposed by Giri et al 39 , of V4 and V8 are 0.09 and 0.03 respectively, which is significantly lower considering the maximum value of VSI (0.96) needed to classify specific variants as being preferentially selected. The lack of texture in martensite and weaker texture of austenite in the as-fabricated condition requires further discussion.…”

Parent grain reconstruction from partially or fully transformed microstructures in MTEX

“…The computational approaches to parent grain reconstruction presented in the scientific literature to date can be roughly divided into two groups using either pixel- (Miyamoto et al, 2010;Bernier et al, 2014;Wang et al, 2019) or grain-level (Cayron et al, 2006;Germain et al, 2012;Gomes & Kestens, 2015;Gomes de Araujo et al, 2021;Pham et al, 2015;Huang et al, 2020;Giri et al, 2019;Ranger et al, 2018) EBSD map data. The first group of methods claim to be more accurate to local changes in the parent orientation, and are apparently superior in identifying annealing twins in austenite and in reconstructing ausformed alloys, whereas the second group of methods are said to be computationally more efficient.…”

“…The first group of methods claim to be more accurate to local changes in the parent orientation, and are apparently superior in identifying annealing twins in austenite and in reconstructing ausformed alloys, whereas the second group of methods are said to be computationally more efficient. Perhaps because the sizes of EBSD maps are rapidly increasing, the most recently developed parent grain reconstruction algorithms from Nyysso ¨nen et al (2018), Huang et al (2020), Giri et al (2019) and Ranger et al (2018) tend to favour the grain-level approach. Consequently, the following paragraphs describe how grain-level parent grain reconstruction methods are implemented in MTEX.…”

“…Following the nucleation stage, a growth algorithm was applied to reconstruct the parent orientation for the remaining child grains. Most grain-level algorithms described by Pham et al (2015), Huang et al (2020), Giri et al (2019) and Ranger et al (2018) are based on this approach and apply various adjustments to improve specific parent grain reconstruction scenarios.…”

“…Humbert et al (1994) focused on child to parent reconstruction in Ti and Zr alloys, and later, Cayron et al (2006) were the first to reconstruct parent austenite from child martensite in steel. Since then, various reconstruction algorithms have been developed [examples include those reported by Miyamoto et al (2010), Germain et al (2012, Gomes & Kestens (2015), Nyysso ¨nen et al (2018), Pham et al (2015), Huang et al (2020), Giri et al (2019), Ranger et al (2018), Bernier et al (2014) and Wang et al (2019)], with each new or modified iteration claiming improved performance in reconstruction accuracy and/or computational efficiency compared with previous implementations.…”