Understanding the interactions of Σ3n boundaries and the triple junction character is important in the context of grain boundary engineering in cubic materials. In a triple junction, when two boundaries are Σ3 and Σ9, the third boundary is either a Σ3 or a Σ27 as per the Σ-combination rule. In the present work, the role of the misorientation axis of the interacting Σ boundaries on the character of the third boundary is systematically studied. The calculated probabilities of occurrences of Σ3, Σ9 and Σ27 boundaries are correlated with the experimental triple junction distributions in Ni and Ni based superalloys. © 2019 Elsevier Inc.

Srikanth Vedantam

Department of Engineering Design

V. Subramanya Sarma

Department of Metallurgical and Materials Engineering

R. Jeyaraam

Grain boundaries

Probability distributions

Annealing twins

COINCIDENCE LATTICES

electron back scatter diffraction

Mis-orientation

Triple junction

Nickel alloys

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Materials Characterization

In this work, the role of grain boundary engineering (GBE) on the weld heat-affected-zone (HAZ) liquation cracking resistance of austenitic stainless steel AISI 316Ti was investigated. Standard wrought-processed alloy 316Ti was cold rolled to 5% strain and subsequently annealed at 1373 K for 30 min to achieve the optimum grain boundary character distribution (GBCD). The GBE samples were found to consist of a significantly higher fraction (72%) of low Ʃ coincident site lattice (CSL) boundaries as compared to the as received (AR) samples (45%). To study the liquation cracking behavior, single-track longitudinal varestraint tests was performed on AR and GBE samples. Microstructural examination revealed that the grain coarsening and the liquation events were less prominent in the GBE samples as compared to the AR samples. It is believed that the reduced segregation of impurities to the special boundaries (coherent Ʃ3 twins, in particular) present in the GBE samples is responsible for the observed improvement in the HAZ liquation cracking resistance. © 2018 Elsevier Inc.

Effect of grain boundary character distribution on weld heat-affected zone liquation cracking behavior of AISI 316Ti austenitic stainless steel

The role of grain boundary engineering (GBE) on high-temperature hot corrosion behavior of alloy 617 was evaluated by exposing both the as-received (AR) and GBE specimens in a salt-mixture of (75% Na2SO4 + 20% NaCl + 5% V2O5) at 1273 K for 24 h. The AR specimen having continuous network of random high angle grain boundaries (HAGBs) has undergone hot corrosion and substantial depletion/segregation of alloying elements through the entire cross section. The GBE specimen exhibited significantly reduced hot corrosion and depletion/segregation of alloying elements. This is attributed to the high fraction of 3-CSL triple junctions which break the percolation in the random HAGBs network. © 2016 Elsevier Ltd.

Corrosion Science

Implication of grain boundary engineering on high temperature hot corrosion of alloy 617

Thermo-mechanical processing (one-step and iterative) comprising strain (5, 10, and 15 pct cold rolling) and annealing [at 1273 K, 1323 K, and 1373 K (1000 °C, 1050 °C, and 1100 °C) for different times of 30 minutes, 1 and 2 hours] were employed to realize a grain boundary engineered (GBE) microstructure in alloy 617. Among the single-step routes, the process employing 15 pct cold reduction and annealing at 1373 K (1100 °C) for 1 hour was found to be effective in increasing the fraction of Σ3 boundaries; however, it also induced partial recrystallization. The iterative processing employing lower reductions and higher annealing temperatures failed to realize GBE microstructure. The second-phase carbides in this material effectively pin the boundaries thus requiring higher pre-strain to initiate the boundary migration and subsequent multiple twinning events. The iterative processing designed based on the outcomes of the single step route resulted in GBE microstructure by significantly increasing the Σ3 fraction and substantially disrupting the random high-angle grain boundaries connectivity. The newly added Σ3 boundaries in the GBE microstructure predominantly terminated on (111) plane indicating that they have low-energy configuration. The GBE specimen has shown remarkable resistance to intergranular corrosion as compared to the as-received condition. © 2015, The Minerals, Metals & Materials Society and ASM International.

Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

Role of Carbide Precipitates and Process Parameters on Achieving Grain Boundary Engineered Microstructure in a Ni-Based Superalloy

The Measurement of Grain Boundary Geometry

Beilstein Journal of Nanotechnology

On the structure of grain/interphase boundaries and interfaces

On the significance of misorientation axes of CSL boundaries in triple junctions in cubic materials

Journal	Data powered by TypesetMaterials Characterization
Publisher	Data powered by TypesetElsevier Inc.
ISSN	10445803
Open Access	No