Role of Interface in Multilayered Composites under Irradiation: A Mathematical Investigation

Abstract

A continuum model of point-defects evolution during irradiation of a multilayer composite material is presented in this work. Nonstationary balance equations are used to describe production, recombination, transport, and annihilation, or removal, of vacancies and interstitials in a --three-layer system ( = Cu and = Nb, V, or Ni). In addition, transport and trapping of point-defects at interfaces are taken into account. Numerical investigation on similarities and differences between Cu/Nb, Cu/V, and Cu/Ni systems is also performed. A general comparison of model results reveals that average vacancy concentration is typically higher than SIA one in both layers for all the systems investigated. This is a consequence of the higher diffusion rate of SIAs with respect to vacancies. Stationary state is reached without saturating interface point-defect traps by all systems but Cu/Ni for the case of SIAs. It can be also seen that Cu/Nb and Cu/V systems have a very similar behavior regarding point-defect temporal evolution in copper (layer ), while higher SIA concentration at steady state is shown therein by the Cu/Ni structure. Moreover, Cu/V system displays the lower stationary vacancy concentration in layer .

Self-healing ability assessment of irradiated multilayered composites: A continuum approach

“…We consider the same system described in our previous work [34], where a layer of metal α is in between two layers of metal β (cf. Figure 1a).…”

“…A point defect may go into an unoccupied trap site, either by a SIA or a vacancy, or recombine with the nearest trapped opposite point defect, jumping there from z possible adjacent sites in the matrix. In our previous work [34], z was set equal to 4 for any material structure according to Brailsford and Bullough's work. Thus, the two interface annihilation mechanisms consisting of a point defect jumping to an unoccupied trap and to an occupied trap by the opposite point defect can be considered to have a prefactor of 1 and 4 respectively.…”

“…In order to obtain dimensionless and normalized equations and parameters, a change of variables has been used in this work following the same procedure reported previously [34]. Dimensionless variables and parameters, as well as scaling and reference values can be found in above work.…”

“…Average dimensionless concentration and net-production rate of the point defect of type j in layer γ, ) (γ χ j and ) (γ Π respectively, as well as dimensionless flux of the point defect of type j from layer γ to the interface between metals α and β, ) (γ j J , have been defined as in our previous work [34] with the aim of illustrating and discussing model results. Model equations are solved by using the commercial software…”

“….4, along with the parameters for Cu, Nb and V reported in our previous work [34] except the value of parameter z , which has been evaluated in next section before setting it, and…”