Hydrogenated vacancies lock dislocations in aluminium

Abstract

Due to its high diffusivity, hydrogen is often considered a weak inhibitor or even a promoter of dislocation movements in metals and alloys. By quantitative mechanical tests in an environmental transmission electron microscope, here we demonstrate that after exposing aluminium to hydrogen, mobile dislocations can lose mobility, with activating stress more than doubled. On degassing, the locked dislocations can be reactivated under cyclic loading to move in a stick-slip manner. However, relocking the dislocations thereafter requires a surprisingly long waiting time of ∼103 s, much longer than that expected from hydrogen interstitial diffusion. Both the observed slow relocking and strong locking strength can be attributed to superabundant hydrogenated vacancies, verified by our atomistic calculations. Vacancies therefore could be a key plastic flow localization agent as well as damage agent in hydrogen environment.

Effects of hydrogen on the mechanical response of X80 pipeline steel subject to high strain rate tensile tests

“…In the hydrogen‐induced ductile‐to‐brittle transition model, it is shown that the aggregation of hydrogen at the crack tip prevents dislocation emission from transgranular fractures. This model is consistent with the phenomena occurring during quantitative mechanical tests on aluminum, which were observed by using an environmental transmission electron microscope …”

“…This model is consistent with the phenomena occurring during quantitative mechanical tests on aluminum, which were observed by using an environmental transmission electron microscope. 8 The hydrogen-induced fracture surfaces of different metals and the hydrogen contents are described in terms of dimples, 9 "quasi-cleavage" 10,11 and flat surfaces, 12 and intergranular facets. 13 Different fracture features have been described by different HE mechanisms.…”

In Situ Transmission Electron Microscopy Characterization and Manipulation of Two‐Dimensional Layered Materials beyond Graphene

“…For the electron beam combined with an electrical field, Wang et al demonstrate a graphene nanoribbon device with semiconducting behavior fabricated by focused electron beam in TEM and tests the electrical performance at the same time . For the mechanical study combined with environmental TEM, Xie et al Alumina pillar mechanical fracture behavior under hydrogen environment together with a force nanoindenter . Beyond imagination, Kalinin et al proposed an exciting concept of building nanomaterials at the atomic level using STEM .…”

Stress corrosion cracking and corrosion fatigue cracking behavior of A7N01P‐T4 aluminum alloy

“…Hydrogen will move along with the dislocations – the dislocation migration of hydrogen has been proven by a large number of experiments . Hydrogen has a pinning effect on dislocation in aluminum alloy and causes high density dislocation in the zones around the crack tip . Therefore, the cathodic reaction produces hydrogen atoms and then enters into the plastic zone and causes the hydrogen‐induced embrittlement of aluminum alloys at the tip of crack.…”