The Role of Thermomechanical Routes on the Distribution of Grain Boundary and Interface Plane Orientations in Transformed Microstructures

Abstract

In the current study, a series of thermomechanical routes were used to produce different microstructures (i.e., ferrite and martensite) in low-carbon low alloy steels. The five-parameter grain boundary character distribution was measured for all microstructures. The thermomechanical processing route altered the texture of the fully ferritic microstructure and significantly influenced the anisotropy of the grain boundary character distribution. Generally, the population of (111) planes increased with an increase in the c-fiber texture for the ferritic microstructure, but it did not change the shape of the grain boundary plane distribution at specific misorientations. The most commonly observed boundaries in the fully ferritic structures produced through different routes were {112} symmetric tilt boundaries with the R3 = 60 deg/[111] misorientation; this boundary also had a low energy. However, the grain boundary plane distribution was significantly changed by the phase transformation path (i.e., ferrite vs martensite) for a given misorientation. In the martensitic steel, the most populous R3 boundary was the {110} symmetric tilt boundary. This results from the crystallographic constraints associated with the shear transformation (i.e., martensite) rather than the low-energy interface that dominates in the diffusional phase transformation (i.e., ferrite).

Texture and Grain Boundary Network Evolution of Laser Powder Bed Fusion Processed Pure Ni During Post-printing Annealing

“…[35,36] The manifestation of a relatively strong 001 h i texture evolved during deposition promotes the termination of planes with a (001) orientation. This is similar to other reports where cubic materials with strong {100}, [18] {101} [17] and {111} [37] texture, stimulate the plane orientation of (100), ( 101) and (111), respectively. The post-printing annealing treatment revealed a significant effect on the overall grain boundary plane distribution.…”

Crystallographic Features of Phase Transformations during the Continuous Cooling of a Ti6Al4V Alloy from the Single-Phase β-Region

“…The α/α-misorientation was mainly dominated by 60° boundaries at a high cooling rates. This was due to the fact that the formation of this boundary is most crystallographically favorable to minimize the transformation strain [ 39 ].…”

“…Moreover, a number of studies have shown the effect of phase transformation paths [ 10 , 18 , 36 ], thermo- and thermomechanical processing [ 37 , 38 , 39 ], and chemical composition [ 40 ] on α/α grain boundary network characteristics (misorientation angle, plane orientation, population, connectivity) and on α precipitation mechanisms. Particularly, diffusion and shear are the two generally accepted phase transformation mechanisms in titanium alloys, which are usually controlled by varying the cooling rates from the single β-state [ 3 ] or (α + β)-field [ 41 ].…”