Grain orientation statistics of grain-clusters and the propensity of multiple-twinning during grain boundary engineering

Publication date: 15 December 2016
Source:Materials & Design, Volume 112
Author(s): Tingguang Liu, Shuang Xia, Baoshun Wang, Qin Bai, Bangxin Zhou, Cheng Su
Large grain-cluster or so-called twin-related domain is a typical characteristic of the grain boundary (GB) engineered microstructure. Grain-cluster is formed via numerous twinning operations starting from single nucleus, and the process is referred to as multiple-twinning. This work investigated the orientation diversity within grain-clusters and the twinning ordering of multiple-twinning based on the statistics of grain-orientations in 30 large-sized grain-clusters from GB-engineered Ni-based alloy 690. The statistics show that the grain-cluster apparently has several dominant orientations. A few dominant orientations occupy most area and most grains in a grain-cluster. Moreover most misorientations between these dominant orientations are of low-order ∑3ⁿ-type (n=1, 2), and the 4 sub-dominant orientations are twinning variants of the first-dominant orientation in most cases. These statistical characteristics of grain-clusters reflect the general behavior of multiple-twinning: back-and-forth pattern and preferential orientations. The twinning operations produce not only higher (forward) but also lower (backward) generation orientations, and the backward probability is higher than the forward. The multiple-twinning shows a propensity to form or access to a few preferential orientations, and results in the formation of dominant orientations of the formed grain-cluster.

Graphical abstract

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