A Preliminary In-situ TEM Study of Martensite/Austenite Interface Migration in an Fe-20Ni-5.4Mn Alloy

In Situ High-Temperature EBSD and 3D Phase Field Studies of the Austenite–Ferrite Transformation in a Medium Mn Steel

“…The actual motion of real α / γ interfaces has been studied experimentally with different in situ techniques such as optical microscopy (OM) (Watanabe et al, 2004; Witusiewicz et al, 2005, 2013), laser scanning confocal microscopy (Phelan et al, 2005; Chen et al, 2013 a ; Cheng et al, 2014; Sainis et al, 2018), scanning electron microscope (SEM)/electron backscattered diffraction (EBSD) (Prior et al, 2003; Seward et al, 2006; van der Zwaag et al, 2006; Fukino & Tsurekawa, 2008; Mishra & Kubic, 2008; Fukino et al, 2011; Torres & Ramírez, 2011; Enomoto & Wan, 2017; Shirazi et al, 2018) photoemission electron microscopy (Middleton & Form, 1975; Middleton & Edmonds, 1977; Edmonds & Honeycombe, 1978), and transmission electron microscopy (Brooks et al, 1979; Moine et al, 1985; Onink et al, 1995; Mompiou et al, 2015; Guan et al, 2017; Liu et al, 2017; Du et al, 2018). Each of these techniques has its own advantages and drawbacks in accurately documenting the interface motion as a function of the imposed external parameters (such as temperature and composition) and the transient local conditions (such as triple junctions where three or more boundaries meet, neighboring interfaces and grain boundaries and overall degree of transformation).…”

Evolution of Microstructure During the In Situ Heating of 42 Pct Cold-Rolled High Mn Steel

“…Very few in situ annealing studies [3,[18][19][20] have been undertaken on high Mn steels using transmission electron microscopy (TEM) to track the reversion mechanisms of e-and a¢-martensite. For an Fe-24Mn-6Si alloy (solution treated at 1000°C for 3600 seconds followed by quenching to produce an e-martensite fraction of 30 pct in the initial austenitic microstructure), in situ TEM heating to 227°C led to e-martensite reversion, which resulted in the formation of c/e-martensite lamellae.…”

“…[21] For an Fe-20Ni-5.4Mn alloy (subjected to prior annealing at 1200°C for 3600 seconds followed by quenching to À 80°C to produce a¢-martensite with lath morphology), in situ TEM heating at 560°C for 135 seconds showed diffusional a¢-martensite reversion via the migration of the c/a¢-martensite interface by the fast motion in the direction normal to the interface and slow lateral motion of ledges on the interface. [18] For an Fe-5Mn-0.2C steel (subjected to prior annealing at 1200°C for 1800 seconds followed by quenching to 28°C to produce a¢-lath martensite), in situ annealing at 650°C for 257 seconds resulted in diffusional reversion of a¢-martensite occurring via the nucleation and growth of c at the a¢-martensite lath boundaries. [22] Our previous ex situ annealing study of high Mn steel tracked the reversion of e-and a¢-martensite to c in multiple samples heated to different temperatures.…”

Autocatalysis, Entropic Aspects and the Martensite Transformation Curve in Iron-Base Alloys

“…Comparing, α X ≈ 1 should reflect a less intense feedback from the relaxation of the transformation strains. We propose that α X ≈ 1 stems from stress-accommodating micro-domains within the martensite unit 14,39,42 as well as from slip during the motion of the martensite-austenite interface [43][44][45] .…”