Deformation behavior of duplex austenite and ε-martensite high-Mn steel

Abstract

Deformation and work hardening behavior of Fe–17Mn–0.02C steel containing ε-martensite within the austenite matrix have been investigated by means of in situ microstructural observations and x-ray diffraction analysis. During deformation, the steel shows the deformation-induced transformation of austenite → ε-martensite → α′-martensite as well as the direct transformation of austenite → α′-martensite. Based on the calculation of changes in the fraction of each constituent phase, we found that the phase transformation of austenite → ε-martensite is more effective in work hardening than that of ε-martensite → α′-martensite. Moreover, reverse transformation of ε-martensite → austenite has also been observed during deformation. It originates from the formation of stacking faults within the deformed ε-martensite, resulting in the formation of 6H-long periodic ordered structure.

Nucleation, coarsening and deformation accommodation mechanisms of ε-martensite in a high manganese steel

“…-type ε-ISFs [27]. In that study, the stacking fault probability of I2 -type ε-ISFs was found to decrease with increasing tensile strain.…”

“…The nomenclature of εmartensite faults used in Ref. [27], which is based on a change in the stacking sequence, is opposite to that used in the present case (which was adopted from Ref. [20]).…”

“…Kim et al [26] observed dislocations with a 〈c〉 component in ε-martensite which dissociate into Shockley partial dislocations in the basal plane to accommodate deformation during tensile testing of an Fe-17Mn steel to 0.05 engineering strain. Using Xray diffraction peak analysis of an Fe-17Mn-0.02C steel, an earlier study suggested that ε-ISFs are behind its reverse transformation back to the γ phase during tensile deformation [27]. In an Fe-14Mn-6Si-9Cr-5Ni shape memory alloy cold-rolled to 10% thickness reduction and annealed at 697 °C for 600 s, the presence of an immobile, 3-5 atomic layers wide, fcc stacking sequence within the ε-martensite phase was reported as the possible reason behind the resistance to shape change during fcc to hcp phase transformations [28].…”

The microstructure of as-quenched 12Mn steel

“…12 While we have not been able to observe the pattern of  martensite in the austenite prior to the transformation to ', it seems reasonable to expect that it resembles that found in alloys with slightly higher Mn content that quench to a mixture of  and . Steels with roughly 17Mn have this behavior [4,20]. Micrographs of the two-phase mixture in 17Mn steels show the prior  densely decorated with a rather uniform mixture of the four  variants, with primary  plates traversing the grain.…”

In Situ Neutron Diffraction Study of Phase Transformation of High Mn Steel with Different Carbon Content

“…The diffraction pattern of high-Mn TRIP steel contains many diffraction peaks, and it is very difficult to separate these peaks to analyze respective deformation behaviors among the various phases. Kwon et al [10,11] studied a similar composition of TRIP steel using in situ neutron diffraction, and they analyzed constituent phases through the whole pattern via the application of the Rietveld method. Although electron backscatter diffraction (EBSD) and conventional X-ray diffraction (XRD) have been extensively used to examine the phase transformations among various phases, these analytical techniques have limitations in obtaining average information from the bulk sample.…”