The role of radiation-induced segregation in defect-phase formation in Ni-Ge and Ni-Si alloys

TL;DR

This study investigates how radiation-induced segregation influences defect and phase formation in Ni-Ge and Ni-Si alloys, revealing distinct microstructural evolutions driven by different defect flux mechanisms.

Contribution

It compares the microstructural evolution of Ni-Si and Ni-Ge alloys under irradiation, highlighting the different roles of interstitial and vacancy fluxes in segregation behavior.

Findings

Ni-Si shows high density of Frank loops

Ni-Ge exhibits complex dislocation arrays

Ni3Ge shell coats He bubbles without Si segregation

Abstract

The interactions between chemical phase fields and structural defects play a key role in the properties of alloys. We illustrate the importance of these interactions in driven alloys, where defects are continuously being created, with particular focus on systems where radiation-induced segregation occurs. Specifically, we compare the microstructural evolution in undersaturated Ni-Si and Ni-Ge alloys during both 100 keV He and 2 MeV Ti irradiations. While the equilibrium phase diagrams of these systems are similar, and both systems show strong radiation-induced segregation, the evolving defect structures are remarkably different. Ni-Si reveals a high density of Frank loops, while Ni-Ge shows a complex array of dislocations. Moreover, a Ni3Ge precipitate shell is observed to coat He bubbles, while no segregation of Si is observed at such bubbles. We explain these differences in behaviors to solute drag by interstitial fluxes in Ni-Si vs solute drag by vacancy fluxes in Ni-Ge.