In Situ Study of Deformation Twinning and Detwinning in Helium Irradiated Small‐Volume Copper

Abstract

The influence of nanoscale helium bubbles on the deformation twinning and detwinning behavior of submicron‐sized Cu is investigated under tension, compression, and cyclic loading. In situ nanomechanical tests performed inside a transmission electron microscope reveal that twinning and detwinning occur readily in helium irradiated copper under both tension and compression. Continuous shearing of helium bubbles by Shockley partials leads to twin formation, whereas the residual back‐stress accumulated from dislocation‐bubble interactions assist in detwinning. These interactions also elevate the critical shear stress for partial dislocation slip in helium irradiated Cu compared to that in fully dense Cu. The growth twin boundaries can significantly enhance the twinning stress in helium irradiated Cu pillar, and deformation twin‐growth twin boundary interaction promotes the formation of internal crack and thus accelerates failure. The effect of crystallographic orientation and sample size on the overall deformation characteristics of helium irradiated Cu is briefly discussed. The current studies show that deformation twinning and detwinning are also active deformation models in helium irradiated small‐volume copper.

Radiation-Induced Helium Bubbles in Metals

“…Hence, nano/micro-mechanical tests are widely adopted to evaluate He bubble induced hardening in these sample. Nanoindentation [63,116,117], and in situ mechanical testing in SEM [118,119,120,121] and TEM [122,123,124,125,126,127] are widely performed to investigate the effect of He bubbles on the mechanical properties of various metals. We mainly focus on three parts next: He irradiation hardening in single-phase metals, He irradiation hardening in metallic multilayers and theoretical modeling of He irradiation hardening.…”

“…We start the discussion with He irradiation hardening in single-phase metals. Several studies are performed on He irradiated steel [63], Ni [120], Cu [118,122,123,124,125,126] and Al–4Cu alloy [127] to evaluate He radiation hardening and interactions of He bubble with dislocations/deformation twin [63,120,121,122,123,124,125,126,127]. Using nanoindentation teats, Roldan et al [63] found that He-irradiated steels after annealing demonstrate much higher hardness compared with as-received samples.…”

New Developments in Nanomechanical Methods

“…23 Within the past decade, development of depth-sensing transmission electron microscopic (TEM) in situ mechanical testing holders 10 has further enhanced our ability to resolve and quantitatively understand nanomechanical phenomena. TEM in situ mechanical testing has been conducted in compression, 24 tension, 19,24 bending, 25 and indentation 26 modes to investigate a wide range of nanomechanical behaviors at the atomic through nano-scale, including dislocation slip, [27][28][29] twinning, 30,31 diffusionless phase transformations, 32 bubble shearing, 30,33 and irradiation effects. 26,34,35 Advancements in computation since the late 1990s have developed in concert with the aforementioned experimental methods.…”

Radiation damage to materials

“…Hence, nano/micro-mechanical tests are widely adopted to evaluate He bubble induced hardening in these sample. Nanoindentation [63,116,117], and in situ mechanical testing in SEM [118][119][120][121] and TEM [122][123][124][125][126][127] are widely performed to investigate the effect of He bubbles on the mechanical properties of various metals. We mainly focus on three parts next: He irradiation hardening in single-phase metals, He irradiation hardening in metallic multilayers and theoretical modeling of He irradiation hardening.…”

“…We start the discussion with He irradiation hardening in single-phase metals. Several studies are performed on He irradiated steel [63], Ni [120], Cu [118,[122][123][124][125][126] and Al-4Cu alloy [127] to evaluate He radiation hardening and interactions of He bubble with dislocations/deformation twin [63,[120][121][122][123][124][125][126][127]. Using nanoindentation teats, Roldan et al [63] found that He-irradiated steels after annealing demonstrate much higher hardness compared with as-received samples.…”