## 1 Introduction
Thus, in order to obtain an alloy with a given maximum shear strength or fatigue resistance, one has to predict theoretically the required particle size distribution of \(\theta^{\prime}\) phase and then to create it in aging of alloys. To describe the plastic deformation of aluminum alloys, the approach is now widely used in which the current flow stress of alloy is described as the sum of several components accounting for the contribution of various hardening mechanisms [39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50]. The following mechanisms of strength are distinguished most often: (1) the inherent strength of matrix, usually this term includes the Peierls barrier of a pure single crystal of aluminum, which is quite low; (2) the strain hardening by forest dislocations in the form of the Taylor relation--this term can include both the kinematic hardening and accumulation of dislocations in the form of the Orowan loops on precipitates; (3) the strengthening by grain boundaries in the form of Hall-Petch relations; (4) the contribution of the solid solution of impurity atoms; and (5) the hardening by precipitates of second phases, where the contribution of both the cuttable and non-cuttable ones is usually considered. Further, these terms are combined according to different mixing rules to give the current state of the flow stress depending on deformation, strain rate and temperature. Some of the above cited works describe the kinetics of precipitation of strengthening phases with a size distribution of inclusions that makes it possible to directly describe the stage of artificial aging [40; 41; 42; 43; 44; 48; 49]. At the same time, the properties of obstacles during plastic deformation are considered to be unchanged, while the experimental works sufficiently convincingly indicate that these changes occur and affect both the strain hardening rate and the strength of the alloy itself. During a mechanical loading of alloys, deformation tends to localize in thin shear bands, in which the properties of material can change faster than the average ones for the bulk of the sample. Therefore, a more accurate approach to describe the properties of alloy implies the use of such a scheme, which explicitly describes the accumulation of deformation in shear bands. A convenient tool for such studies is the introduction of constitutive equations for alloy strength into continuum mechanics equations with numerical realization based on the finite-difference or finite-element schemes [9; 11; 12; 51; 52; 53]. In these works, the models of strength of alloys include various factors, but the properties of hardening inclusions remain constant. However, the cutting of inclusions obviously leads to a change in their properties. Another widely used meso-scale approach is the discrete dislocation dynamics, which allows one to investigate for a representative dislocation ensemble the details of dislocation-dislocation interaction, strain hardening [54] and dislocation-precipitate interaction [55; 56; 57], but precipitates are still treated as unchanged and impenetrable by dislocations. The interaction of dislocations with nano-sized inclusions in the Al-Cu system was studied by a number of authors using MD modeling [33; 34; 35; 57; 58; 59; 60; 61; 62; 63]. It was demonstrated that even for the same type of inclusion, different mechanisms of overcoming are realized, for example, for single-layer GP zones, an increase in precipitate diameter leads to the realization of Orowan looping instead of cutting mechanisms [58]; also, it was demonstrated in [61] that a change in the mechanism can occur even for one size of precipitate, but at different temperatures and strain rates. The change of overcoming mechanisms was registered with MD simulations for such stiff inclusions, as \(\theta^{\prime}\), \(\theta^{\prime}\) phases.