Vacancy injection

The enhancement of creep by anodic dissolution is well known, for copper in acetic acid153 and austenitic stainless steels and nickel-based alloys in pressurized water reactor (PWR) environments. The initial vacancy injection from the surface is followed by vacancy attraction to the inside dislocations, which promotes easier glide, climb, and crossing of microstructural barriers. This mechanism illustrates the corrosion-enhanced plasticity approach.95... 

Film-induced cleavage models. It has been suggested that dealloying and/or vacancy injection could induce brittle fracture. The model assumes that a brittle crack initiates in a surface film or layer and this crosses the film/matrix without loss of speed. The brittle crack will continue in the ductile matrix until it eventually blunts and arrests. Verification of this model needs better understanding of the surface films and brittle fracture. (Jones)5... 

Figure 20. Model boundary interphase exchange currents involving lattice vacancy injection at the compound-electrolyte interface and vacancy exchange into the metal releasing an electron and transferring a metal ion into the compound layer (12)...

In this reaction, the cation vacancies are annihilated at the scale-metal interface. Sometimes, the reaction at the interface is described as vacancy injection, that is, a transfer of cation vacancies to persist as metal vacancies V, in the metal lattice... 

Most of the EAC mechanisms assume that the main role of the surface film is to localize, directly or indirectly, the damage inflicted to the material by the environment, i.e., general or selective dissolution, vacancy injection, modification of the interaction of dislocations with surface layers (image force effects), and hydrogen absorption. 

Revie and Uhlig, 1974). The initial vacancy injection from the surface is followed by vacancy attraction to the inside dislocations, which promotes easier glide, climb, and crossing of microstructural barriers. 

Vacancy injection because the outward diffusive flux of alloying elements undergoing selective oxidation (e.g., chromium) must be counterbalanced by an inward flux of vacancies. This is generally referred to as the Kirkendall effect, and it is possible for the injected vacancies to eventually supersaturate the alloy matrix and coalesce to form voids. The Kirkendall effect might also operate in the diffusion of surface-enriched, non-reacting elements back into the alloy. 

Vacancy injection, a phenomenon usually considered to be characteristic of cationic scale growth, was a rather popular topic after the mid-1990s. This phenomenon is again often invoked to explain the formation of pores and cavities within the metallic substrate beneath an oxide scale such as NiO or FeO and, more recently, AI2O3 for the oxidation of intermetallic aluminides. In that case, the metal-oxide interface is assumed to be unable to move freely to follow the recession of the metal lattice. Reaction [2.3] must then be replaced by the following reaction ... 

This phenomenon of vacancy injection is commonly considered to be restricted to cationic growing scales. However, vacancy injection could also... 

Francis R and Lees D G (1989), Evidence for vacancy injection during the oxidation of iron , Mat Sci Eng A, A120-A121, 97-99. 

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