Shih-Yuan LuYung-An ChenChien-Yu TsengTsai-Fu ChungYo-Lun YangJia-Jun ChenCheng-Ling TaiTzu-Ching TsaoPo-Han ChiuChih-Yuan ChenR.D.K. MisraTE-CHENG SUJer-Ren Yang2025-01-032025-01-032025-0209215093https://www.scopus.com/record/display.uri?eid=2-s2.0-85212213082&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/724532Massive ferrite and allotriomorphic ferrite have respectively been produced in interstitial-free steel samples (with a chemical composition of Fe-0.001C, wt.%) by water-quenching (WQ) and furnace-cooling (FC) from the austenite region. The primary objective of the present work is to define the relationship between the deformation structures and mechanical behaviors in massive ferrite (WQ-treated) and allotriomorphic ferrite (FC-treated) specimens. To accomplish the object, we have uniquely combined transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) to illuminate the detailed deformation structures in the hope that the study will potentially extend the application of massive ferrite steels. In the FC-treated specimen, large-sized allotriomorphic ferrite grains with smooth boundaries were observed, whereas in the WQ-treated specimen, massive ferrite grains with intragranular substructures and ragged grain boundaries were found. It was noted that the degree of misorientation within the massive ferrite grains was significantly greater than that within the allotriomorphic ferrite grains, which was consistent with the fact that there were more sub-boundaries and dislocations in the massive ferrite grains. This distinct microstructure of the massive ferrite grains contributed to the yield strength of 138 MPa and ultimate tensile strength of 290 MPa in the WQ-treated specimen. In the allotriomorphic ferrite specimen, the yield strength (∼121 MPa) and ultimate tensile strength (∼269 MPa) were 14.1 % and 7.8 % lower than those of the massive ferrite specimen. The total elongation of both steels was similar, about ∼41–43 %. Interrupted tensile strain experiments at different strains (0.05, 0.1, 0.2, 0.3 and 0.4) followed by post-deformation electron microscopy provided strong evidence that microbands develop appreciably earlier in massive ferrite specimens than in allotriomorphic ferrite specimens, resulting in a superior work hardening capability.falseElectron backscattered diffraction (EBSD)Interstitial-free steelMassive ferritePhase transformationTransmission electron microscopy (TEM)journal article10.1016/j.msea.2024.1476482-s2.0-85212213082