Surface relief effects associated with the formation of grain boundary allotriomorph in an Fe–C alloy

• Published in: Acta materialia Vol. 46; no. 8; pp. 2929 - 2936
• Main Authors: Bo, Xiang-Zheng, Fang, Hong-Sheng
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.05.1998; Elsevier Science
• Subjects: Applied sciences; Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Metals. Metallurgy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Grain boundaries; Austenitizing; Phase transformations; Austenite; Roughness; Metallography; Steels; Experimental study; Microstructure; STM; Heat treatments; Relief
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/S1359-6454(97)00482-5

Surface relief effects associated with the formation of grain boundary allotriomorph (GBA) in an Fe–C alloy have been first studied by scanning tunneling microscopy (STM). It was discovered that the GBAs which exhibit the surface relief are only developed into one austenite grain, which means the interface between the austenite and the GBA which exhibits surface relief is partially coherent, and the interface between the austenite and the GBA nucleated at the same grain boundary but developed into the adjacent austenite grain may be incoherent. The maximum shape deformation of surface relief due to GBA precipitation is ca. 0.39, which is consistent with that of Widmanstätten ferrite plates. Accompanying the formation of Widmanstätten sawteeth, surface relief is produced, which is composed of reliefs associated with several sideplates. By STM the boundaries between GBAs are clear, which indicates that they are resulted from edge-to-edge (ETE) or face-to-face (FTF) sympathetic nucleation. Super ledges ( ca. 300 nm high) were observed on the broad face of GBA. All these results can be rationally interpreted by the sympathetic nucleation-ledgewise growth mechanism.