Massive 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.

中文翻译：

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无间隙钢中块状和同素异形铁素体的力学行为与变形结构之间的关系


通过奥氏体区域的水淬 （WQ） 和炉冷却 （FC） 分别在无间隙钢样品 （化学成分为 Fe-0.001C， wt.%） 中生产了块状铁素体和同素异形铁素体。这项工作的主要目标是定义块状铁氧体（WQ 处理）和同种异形铁氧体（FC 处理）试样的变形结构和机械行为之间的关系。为了实现这一目标，我们独特地将透射电子显微镜 （TEM） 和电子背散射衍射 （EBSD） 相结合，以阐明详细的变形结构，希望这项研究有可能扩展大块铁素体钢的应用。在 FC 处理的试样中，观察到具有光滑晶界的大尺寸同种异形铁氧体晶粒，而在 WQ 处理的试样中，观察到具有晶内亚结构和参差不齐晶界的块状铁氧体晶粒。值得注意的是，块状铁氧体晶粒内的取向差程度明显大于同素异形铁氧体晶粒内的取向差程度，这与块状铁氧体晶粒中子边界和位错更多的事实一致。块状铁素体晶粒的这种独特微观结构导致 WQ 处理试样的屈服强度为 138 MPa，极限拉伸强度为 290 MPa。在同素异形铁氧体试样中，屈服强度 （∼121 MPa） 和极限抗拉强度 （∼269 MPa） 分别比块状铁氧体试样低 14.1 % 和 7.8 %。两种钢的总伸长率相似，约为 ∼41-43 %。不同应变（0.05、0.1、0.2、0.3 和 0.4） 随后的变形后电子显微镜提供了强有力的证据，表明块状铁氧体样品中的微带明显早于同种异形铁氧体样品，从而获得了优异的加工硬化能力。