Precipitation during high temperature aging of Al−Cu alloys: A multiscale analysis based on first principles calculations

Abstract

Precipitation during high temperature aging of Al−Cu alloys is analyzed by means of the integration of classical nucleation theory and phase-field simulations into a multiscale modelling approach based on well-established thermodynamics principles. In particular, thermal stability of θ'', θ' and θ precipitates was assessed from first principles calculations of the Helmholtz free energy while homogeneous and heterogeneous nucleation of θ'' and θ' was analysed using classical nucleation theory. Precipitate growth was finally computed by means of mesoscopic phase-field model. The model parameters that determine quantitatively the driving forces for each transformation were obtained by means of first principles calculations and computational thermodynamics. The predictions of the models were in good agreement with experimental results and provided a comprehensive understanding of the precipitation pathway in Al−Cu alloys. It is envisaged that the strategy presented in this investigation can be used in the future to design optimum microstructures based on the information of the different energy contributions obtained from first principles calculations.

Ageing response of cold-rolled Al–Cu–Mg alloy

“…Second, the superposition of long-range elastic strain fields originating from dislocations and the θ 0 -phase nucleated on these dislocations decreases the increase in σ YS under peak ageing. The lattice dislocations facilitate the formation of θ 0 -phase plates with minimal volume and shape changes because the elastic strain energy plays a dominant role compared with the interface energies in the nucleation [40,41]. The independence of the θ 0 -phase AR from the pre-strain indicates that the pre-strain has no effect on the basic mechanisms that control the nucleation of this phase [41,42].…”

“…The lattice dislocations facilitate the formation of θ 0 -phase plates with minimal volume and shape changes because the elastic strain energy plays a dominant role compared with the interface energies in the nucleation [40,41]. The independence of the θ 0 -phase AR from the pre-strain indicates that the pre-strain has no effect on the basic mechanisms that control the nucleation of this phase [41,42]. The superposition of the long-stress fields originated from the dislocations, θ 0 -phase plates and the Ω II -phase reduces the overall elastic strain under peak ageing.…”

“…As a result, the increase in σ YS is due to the decreased peak ageing (46 MPa) at an ε of ~0.51. In addition, the internal elastic stress fields affect the growth mechanism strongly [41,42]. As a result, the θ 0 -phase growth depends on the dislocation density.…”

“…The coarsening of the θ 0 -phase under over-ageing leads to loss of coherency of its broad interfaces, whereas the edges of the plates of this phase become incoherent [22]. Moreover, the strengthening efficiency of this particle decreases owing to a decreasing misfit strain, which provides a significant contribution to the extensive softening behaviour at ε � 0.51 [30,41].…”

Quantitative Shape-Classification of Misfitting Precipitates during Cubic to Tetragonal Transformations: Phase-Field Simulations and Experiments

“…The ratio between coherent and semi-coherent interfaces is reported to be in the range of 2–3. The interfacial energy of the coherent interface is reported to be in the range of 150–250 mJ/m 2 [ 7 , 8 , 44 , 47 ]. Table 2 gives the used material data for the γ″ phase in a Ni-rich matrix at 730 °C as well as for the θ′ phase in an Al-rich matrix at 230 °C.…”