Hierarchical structures in cold-drawn pearlitic steel wire

Xiaodan Zhang, Andrew Godfrey, Niels Hansen, Xiaoxu Huang

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Abstract

The microstructure and crystallography of drawn pearlitic steel wires have been quantified by a number of electron microscopy techniques including scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction and nanobeam diffraction, with focus on the change in the structure and crystallography when a randomly oriented cementite structure in a patented wire during wire drawing is transformed into a lamellar structure parallel to the drawing axis. Changes in the interlamellar spacing and in the misorientation angle along and across the ferrite lamellae show significant through-diameter variations in wires drawn to large strains ⩾ 1.5. The structural evolution is hierarchical as the structural variations have their cause in a different macroscopic orientation of the cementite in the initial (patented) structure with respect to the wire axis. The through-diameter variations subdivide the lamellar structure into two distinctly different types: one (called A_A) has a smaller interlamellar spacing and smaller dislocation density than the other (called A_BC). During drawing, the thickness of the ferrite and cementite lamellae are reduced to 20 and 2 nm, respectively, and high-angle boundaries form in the A_BC structure parallel to the cementite lamellae. The structural and crystallographic analyses suggest that boundary strengthening and dislocation strengthening are important mechanisms in the cold-drawn wire. However, differences in structural parameters between the A_A and the A_BC structure may affect the relative contributions of the two mechanisms to the total flow stress.
Original languageEnglish
Title of host publicationFinal programme. 2nd Summer School and Symposium on Nanometals
Number of pages1
Publication date2013
Publication statusPublished - 2013
Event2nd Summer School and Symposium on Nanometals - Weihai, China
Duration: 19 Aug 201323 Aug 2013
Conference number: 2

Conference

Conference2nd Summer School and Symposium on Nanometals
Number2
CountryChina
CityWeihai
Period19/08/201323/08/2013

Bibliographical note

The authors thank NV Bekaert SA Technology Center Laboratory (Zwevegem, Belgium) for the supply of the pearlitic steel wires used in this investigation. The authors gratefully acknowledge the support from the Danish National Research Foundation (Grant No DNRF86-5) and the National Natural Science Foundation of China (Grant No. 51261130091) to the Danish-Chinese Center for Nanometals, within which this work has been performed.

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