New perspectives on twinning events during strain-induced grain boundary migration (SIBM) in iteratively processed 316L
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New perspectives on twinning events during straininduced grain boundary migration (SIBM) in iteratively processed 316L stainless steel Nitin Kumar Sharma1,2,* and Shashank Shekhar1 1 2
Department of Materials Science and Engineering, Indian Institute of Technology Kanpur, U.P., Kanpur 208016, India Present address: Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G1H9, Canada
Received: 4 May 2020
ABSTRACT
Accepted: 7 August 2020
Characterization of microstructure and grain boundary character distribution (GBCD) during iterative thermo-mechanical processing (TMP) of 316L stainless steel were done using electron backscatter diffraction (EBSD). Results from EBSD scans were analyzed in terms of the fraction of special boundaries, their deviation from ideal misorientation, connectivity of random high-angle grain boundaries, and grain size. In order to understand the efficacy of the iterative processing route leading to a well-connected twin boundary network, additional analysis was done in terms of twin-related domain statistics and triple junction distribution. Results from these analyses show that initial iteration results in a microstructure with insufficient twin boundary density, and a poor twin boundary network. Although the next iteration leads to a small increase in twin statistics, it also does not significantly improve the statistics of favorable grain boundaries and their network. However, the fourth iteration of the processing results in a large improvement in both the population and distribution of favorable grain boundaries. All the subsequent iterations were found to result in microstructural deterioration in terms of both population and network of these grain boundaries. Based on the analysis, role of underlying mechanisms such as strain-induced grain boundary migration and static recrystallization in the effective optimization of GBCD was analyzed. The present research gives important insights into these mechanisms and their control during TMP in order to achieve an engineered microstructure.
Springer Science+Business
Media, LLC, part of Springer Nature 2020
Handling Editor: N. Ravishankar.
Address correspondence to E-mail: [email protected]; [email protected]
https://doi.org/10.1007/s10853-020-05240-y
J Mater Sci
GRAPHIC ABSTRACT
Introduction Grain boundary design and control is known to optimize the grain boundary character distribution of the low-stacking fault energy FCC materials in order to improve the grain boundary-related properties and phenomena [1–5]. Some of these phenomena include diffusion and segregation of elements [6], precipitation [7], intergranular corrosion [8–10] and cracking [11, 12], and grain boundary sliding [13]. Formation of annealing twins or R3 CSL boundaries [14] and their spatial distribution and mutual connectivity [15–17] are at the core of the GBCD optimization process. Several research works have attempted different thermo-mechanical processing (TMP) routes in order to either generate new annealing twins or rearrange
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