The Role of Parent Phase Topology in Double Young–Kurdjumow–Sachs Variant Selection during Phase Transformation in Low-Carbon Steels

Abstract

The present paper investigates the role of parent phase topology on a crystallographic variant selection rule. This rule assumes that product phase nuclei appear at certain grain boundaries in the parent structure, such that a specific crystallographic orientation relationship is observed with both parent grains at either side of the grain boundary. The specific crystallographic orientation correspondence considered here is the Young–Kurdjumow–Sachs (YKS) orientation relationship <112>90° (which exhibits 24 symmetrical equivalents). The aforementioned relationship is characteristic of phase transformations in low-carbon steel grades. It is shown that, for different parent phase textures, ~20% of the grain boundaries comply with the double YKS condition allowing for a tolerance of 5°, ignoring the presence of topology in the parent phase microstructure. The presented model allows for connecting the presence of a specific parent phase topology with the condition of the double YKS variant selection rule in a number of practical cases: (i) for hot rolled Ti–Interstitial Free (IF) steel with and without Mn addition, (ii) for cold rolled IF steel exhibiting very strong texture memory after forward and reverse α ⇌ γ phase transformation and (iii) for a martensitic transformation in a Fe–8.5% Cr steel. It is shown that the double YKS variant selection criterion may explain several specific features of the observed transformation textures, while assuming a non-correlated arbitrary pair topology of the parent austenite structure (implying that for N parent orientations N/2 pairs are selected in an arbitrary manner).

Crystallography of Recrystallization in Al and Cu with Fiber Texture

“…For both types of phase transformations, including shear (martensitic) transformations and diffusion-controlled transformations, the orientation relationship is obeyed for the crystal lattices of the original and resulting phases, which is expressed in the parallelism of closed-packed planes and directions. This strict relationship results in the nucleation of the resulting phase on the appropriate grain boundaries serving as a substrate and, therefore, determining the crystallographic texture formed in the process of phase transformation [25,26,52]. Special misorientations serve as orientation relationships in the case of structural transformations, and the special boundaries play the role of substrate.…”

“…Thus, the evolution of the entire system is defined by the process of grain boundary formation. Thus, the possibility and direction of recrystallization processes and phase transformations [24][25][26] depend on the orientation of the neighboring grains.…”

Role of Grain Size and Recrystallization Texture in the Corrosion Behavior of Pure Iron in Acidic Medium

“…Furthermore, the holding time of our annealing treatment routes is quite big for the austenitic variants to undergo grain growth and also change the topology. This means that, during the cooling, the FCC variants will not go back to the original BCC orientations, e.g., see the recent study of Kestens et al [23], since the topology has changed. As for the grain size, 1100 °C annealing enables higher growth rates and thereby larger austenite grain sizes than at 950 °C, resulting in a coarser ferrite microstructure.…”

The Effect of Cooling Rate on Crystallographic Features of Phase Transformations in Zr-2.5Nb

“…Additionally, the structural-textural inheritance during multiple phase transformations was demonstrated at the Ti-6Al-4V alloy in [ 37 ]. In [ 38 , 39 , 40 ], similar texture inheritance in steels and bronzes is explained by the formation of new phase nuclei on crystallographically ordered boundaries near the coincidence site lattice (CSL) boundaries (e.g., ∑3, ∑33, etc. ), which arise in the material as a result of prior deformation (between stable deformation orientations) or due to phase transformations realized in accordance with the OR.…”