Twin related domains in 3D microstructures of conventionally processed and grain boundary engineered materials

Abstract

a b s t r a c tThe concept of twin-limited microstructures has been explored in the literature as a crystallographically constrained grain boundary network connected via only coincident site lattice (CSL) boundaries. The advent of orientation imaging has made classification of twin-related domains (TRD) or any other orientation cluster experimentally accessible in 2D using EBSD. With the emergence of 3D orientation mapping, a comparison of TRDs in measured 3D microstructures is performed and compared against their 2D counterparts. The TRD analysis is performed on a conventionally processed (CP) and a grain boundary engineered (EM) high purity copper sample that have been subjected to successive anneal procedures to promote grain growth. The EM sample shows extremely large TRDs which begin to approach that of a twin-limited microstructure, while the TRDs in the CP sample remain relatively small and remote.

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

“…[10-12, 29, 30], so all the inner grains of a cluster are twins or twins of twins and so on of the nucleus (parent grain), and they could be reconstructed as a tree-shape twin-chain [11,24]. On the other hand, the process of multiple-twinning can be demonstrated as a twin-chain of orientations [11,[24][25][26], as shown in Fig. 4a.…”

“…Based on the formation mechanism of grain-cluster, i.e. the multiple-twinning, the relationship of orientations in a grain-cluster can be reconstructed as a tree-shape twin-chain [11,25,26], as shown in Fig. 4a.…”

“…The proportion of twin-boundaries could be increased to more than 60% from about 40% by the treatment of GB-engineering [11,12,[17][18][19][20][21], because the face-centered-cubic law stacking-fault-energy metals, such as Ni-based alloys, austenitic stainless steel and brass, are prone to twinning [1,2] in the wake of migrating of the recrystallization front boundaries during annealing. The iterative process of twinning operations starting from a single nucleus is referred to as multiple-twinning [21][22][23][24][25], and the generated annealing twins can be reconstructed as a twinning tree, which is referred to as twin-chain [8,11,22,26,27]. The assembly of all grains in the tree is named grain-cluster or twin-related-domain [8,11,12,24,26].…”

“…The iterative process of twinning operations starting from a single nucleus is referred to as multiple-twinning [21][22][23][24][25], and the generated annealing twins can be reconstructed as a twinning tree, which is referred to as twin-chain [8,11,22,26,27]. The assembly of all grains in the tree is named grain-cluster or twin-related-domain [8,11,12,24,26]. All inner grains of the grain-cluster have ∑3 n (n=1, 2, 3…) mutual misorientations, and all inner boundaries are types of ∑3 n but outer boundaries are crystallographically random.…”

Tracking the evolution of intergranular corrosion through twin-related domains in grain boundary networks

“…A more recent approach to the characterization of GB networks in heavily twinned microstructures is the use of the following descriptors: twin-related grain clusters or twin-related domains (TRD). [18][19][20][21][22][23] Gertsman et al 24 defined a twin-related grain cluster as a region of a microstructure in which all of the GBs within a given cluster of grains are described by a Σ3 n (n ≥ 1) misorientation. Fang et al 25 and Xia et al 26 implement the grain cluster analysis in studies of GBE stainless steel and Ni-based Alloy 690, respectively.…”