Effects of initial microstructure on the grain boundary network during grain boundary engineering in Hastelloy N alloy

Abstract

Grain boundary engineering (GBE) was carried out on Hastelloy N alloy which is an important structural material used for molten salt reactor. The proportion of low Σ coincidence site lattice (CSL) grain boundaries of the Hastelloy N alloy can be enhanced to more than 70% with the formation of large-size highly-twinned grain-cluster microstructure which was formed through extensive multiple twinning events during recrystallization. The effects of cold deformation amounts and subsequent annealing on the grain boundary character distribution (GBCD) were investigated. The effects of initial grain size and the primary carbide distribution which was affected by the content of silicon on the grain boundary network evolution were discussed. It was determined that the initial grain size and primary carbide distribution will affect the recrystallization kinetics and hence influence the formation of highly twinned grain-cluster microstructure and the GBCD. The particle stimulated nucleation (PSN) caused by the primary carbides has a detrimental effect on the promotion of low Σ CSL grain boundaries.

Microstructure Evolution and Mechanical Properties of a Powder Metallurgy Ti‐22Al‐25Nb Alloy Processed through Isothermal Rolling and Solution and Aging Treatment

“…This figure reveals that the alloy rolled at high rolling temperature has large grain sizes after solution treatment. Grain growth is caused by GB migration . However, grain growth is not obvious because the solution temperature is close to the temperature of the three‐phase region.…”

“…Grain growth is caused by GB migration. [30] However, grain growth is not obvious because the solution temperature is close to the temperature of the threephase region. A certain amount of α 2 phases exists at the GB and inside the grain, and the pronounced pinning effect of α 2 relative to the GB [31] inhibits the migration of GBs and results in the slow increase in grain size.…”

Roles of Inclusion, Texture and Grain Boundary in Corrosion Resistance of Low-Nickel Austenite Stainless Steel Containing Ce

“…22) As a special low-energy boundary, twin boundaries (∑3 n boundaries) occupying a larger area fraction in austenitic stainless steel are active interfaces relative to the regular crystal structure. 23,24) When the multiple twins meet together, ∑3 boundaries can grow up and form between them due to the effect of interface migration. A twin relationship (60°< 111 > ) of {111} < 110 > and {111} < 112 > orientations constitutes twin boundaries, endowed with high migration rate due to low energy, which is beneficial to the nucleation of {111} < 110 > and {111} < 112 > components.…”

Characterization of Special Grain Boundaries and Triple Junctions in CuxNi1‐x Alloys upon Deformation and Annealing

“…Different ways to achieve a high amount of 3‐GBs have been developed, as have various ways to describe the microstructure, such as by GB character distributions by TJs or by so‐called “twin‐related‐domains” …”