The Effects of Stacking Fault Energy on Radiation Induced Defects in High-entropy Alloys
DescriptionHigh-entropy alloys (HEAs), as emerging alloys composed with four or more principal elements in equal-molar or near equal-molar constituents, open a new way to design alloys and draw great attention in material science. Due to their excellent mechanical property in high temperature, great corrosion resistance, and strong oxidation resistance, HEAs have been proposed as the candidate for structural materials in advanced nuclear systems. What’s more, their promising damage tolerance under heavy ion radiation have been demonstrated by academics from Oak Ridge National Laboratory and University of Michigan in US. Their results show that after Ni-ion irradiation at 773 K, the void swelling in NiFe and NiCoFeCr was one or two orders of magnitude lower than in Ni and NiCo. This effect is explained by reduced dislocation mobility, which leads to the slower growth of large dislocation structures. Similarly, the FeNiMnCr HEA has also show better radiation resistance than Fe-Cr-Ni austenitic alloys under Ni ion irradiation because of smaller dislocation loops formation and undetectable voids.In crystalline materials, the radiation-induced defects is the origin of radiation damage and materials degradation. Upon different dose levels and radiation temperatures, the vacancy-interstitial pairs (Frenkel pairs) produced by high energy particles, will evolve into various defects, such as isolated vacancies and interstitials, black dots (clusters of vacancies or interstitials), dislocation loops and lines, stacking fault tetrahedral (SFT), voids or bubbles. It has been known that, the stacking fault energy (SFE) is a key factor affecting the formation of plane defects. Meanwhile, recent studies have shown that the very low SFE is the one of the most unique characters of HEAs, which is responsible for the special deformation mechanism at room temperatures and cryogenic temperatures. Therefore, it is easy to suppose that the SFE would have strong effect on the evolution of radiation induced defects in HEAs. However, the evolution of radiation induced defects in HEAs has never been systematically evaluated form the perspective of SFE, this relationship is even unclear in the conventional materials.In this proposed work, we aim to explore the effects of SFE on the evolution of radiation induced defects in the HEAs. Our long-term goal targets to develop HEAs as the novel candidate structure materials for advanced nuclear reactors. Based on the above concepts, we will design the HEAs with different SFE, and irradiate them to different dose level by ion accelerator. The radiation induced defects would be subsequently analyzed through Transmission Electron Microscopy (TEM) and Atom Probe Tomography (APT), meanwhile atomic simulation will be conducted to reveal the underlying mechanism. After all, three scientific issues could be expected to address in this work. The first one is the variation of SFE in HEAs by tuning the minor alloying elements. The second issue is the characteristics of radiation induced defects formed in HEAs at different irradiation condition. For the third issue, the effects of SFE on the evolution of radiation induced defects would be revealed. Finally, we will draw a metallurgical guideline for the development of the radiation tolerant alloys via tuning the materials’ SFE.
|Effective start/end date||1/01/19 → …|