Understanding plasticity in irradiated alloys through TEM in situ compression pillar tests

Haozheng J Qu,Matthew J Swenson,Janelle P Wharry,Kayla H Yano,Priyam V Patki

doi:10.1557/jmr.2019.295

Abstract

Depth-sensing transmission electron microscopic (TEM) in situ mechanical testing has become widely utilized for understanding deformation in irradiated materials. Until now, compression pillars have primarily been used to study the elastic properties and yield of irradiated materials. In this study, we utilize TEM in situ compression pillars to investigate plastic deformation in two ion-irradiated alloys: Fe–9% Cr oxide dispersion strengthened (ODS) alloy and nanocrystalline Cu–24% Ta. We develop an algorithm to automate the extraction of instantaneous pillar dimensions from TEM videos, which we use to calculate true stress–strain curves and strain hardening exponents. True stress–strain curves reveal intermitted plastic flow in all specimen conditions. In the Fe–9% Cr ODS, intermitted plastic flow is linked to strain bursts observed in TEM videos. Low strain hardening or strain softening is observed in all specimen conditions. TEM videos link the strain softening in irradiated Fe–9% Cr ODS to dislocation cross-slip, and in Cu–24% Ta to grain boundary sliding.

Highlights

Depth-sensing nano-/micro-mechanical testing of irradiated and radioactive materials has become widely utilized in scanning electron microscopic (SEM) and transmission electron microscopic (TEM) in situ configurations [1, 2, 3]
We have analyzed the plastic deformation of as-received and irradiated Fe–9% Cr ODS and nanocrystalline Cu–24% Ta, following TEM in situ compression pillar testing
We have developed an algorithm to automate the measurement of instantaneous pillar dimensions, which enabled us to generate true stress–strain curves for each pillar

Summary

Introduction

Depth-sensing nano-/micro-mechanical testing of irradiated and radioactive materials has become widely utilized in scanning electron microscopic (SEM) and transmission electron microscopic (TEM) in situ configurations [1, 2, 3]. An advantage of these in situ methods is that the experimentalist can obtain quantitative load–displacement data alongside realtime video that informs deformation phenomena at SEM/TEM resolutions.

Methods

Results

Discussion

Conclusion