BARC/PUB/2021/0943

 
 

Chemical ordering as a precursor to formation of ordered delta-UZr2 phase: a theoretical and experimental study

 
     
 
Author(s)

Ghosh, P. S.; Arya, A.; Basak, C. B.; Poswal, A. K.; and others
(MMD)

Source

Journal of Physics-Condensed Matter, 2021. Vol. 33: Article no. 254003

ABSTRACT

A combination of special quasi-random structure (SQS) analysis, density functional theory (DFT) based simulations and experimental techniques are employed in determining the transformation pathway for the disordered γ-(U, Zr) phase (bcc structure) to transform into the chemically ordered δ-UZr2 phase (C32, AlB2 type structure). A novel Monte-Carlo based strategy is developed to generate SQS structures to study the βω displacive phase transformation in A1−xBx binary random alloy. Structures generated with this strategy and using DFT calculations, it is determined that (222)bcc plane collapse mechanism is energetically unfavorable in chemically disordered environment at UZr2 composition. A mechanically and dynamically stable 24 atom SQS structure is derived which serves as a structural model of chemically ordered δ-UZr2 structure. Finally, a thermodynamic basis for the mechanism of the γ to δ transformation has been estab lished which ensures chemical ordering is a precursor to the subsequent displ acive transformation to form chemically ordered δ-UZr2 structure.

 
 
SIRD Digital E-Sangrahay