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

Abstract

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 © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ grain-cluster. Moreover most misorientations between these dominant orientations are of low-order ∑3 n -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.

Twins and twin-related domains in a grain boundary-engineered 304 stainless steel

“…The sizes range from 37 to 44 μm, and the average grain size for the 14 maps is 41 μm. If the twin-related ( 3 n -type) boundaries were excluded from the size calculation, the sizes of TRDs (TRDs) were obtained [28,[32][33][34][35][36][37]. The result is showed in Figure 4(b).…”

“…For example, Lind et al [27] explored the TRDs in conventionally processed and GB-engineered copper, obtaining that the numbers of grains of the largest TRDs in GBE samples are nearly 10 times more than that of conventional samples. TRD can be topologically represented by a tree-shape twin-chain [27,28,32,34,35], which is closely correlated with multiple-twinning [14,27,32,34] that is the process to form the TRD. However, overall these studies were based on two-dimensional (2D) characterisation on cross-sections except a recent study performed by Lind et al [27] who compared the three-dimensional (3D) TRDs of GBE and conventional copper.…”

Evolution of grain boundary character distributions in alloy 825 tubes during high temperature annealing: Is grain boundary engineering achieved through recrystallization or grain growth?

“…In order to analyze the mutual misorientations between any two grains inside of the cluster, eight grains were randomly selected, and the results are listed in Table II and Table III. The detailed analyzing of all the mutual misorientations between any two grains in the grain-cluster was reported elsewhere [23,33] . It can be demonstrated that all grains in cluster have ∑3 n misorientations regardless of whether they are adjacent.…”

Effect of Twin Spacing and Loading Mode on Mechanical Properties and Deformation Mechanism of NiCoAl Columnar Polycrystalline Alloy

“…This has a positive and important guiding significance for the preparation of nanocrystalline alloys with excellent comprehensive properties of high strength and high plasticity. [3] In addition, the short-range ordered structure of multielement alloys, such as medium-entropy alloys and high-entropy alloys, makes them have good properties and plays an increasingly important role in various industrial products and applications. [4] Adding light-alloy Al into the superalloy Ni-Co alloy can design and prepare NiCoAl medium-entropy alloy with good hightemperature resistance, wear resistance, oxidation resistance, low density, lightweight, high magnetism, and good wave absorption performance.…”

“…This has a positive and important guiding significance for the preparation of nanocrystalline alloys with excellent comprehensive properties of high strength and high plasticity. [ 3 ]…”