A multidisciplinary approach to study precipitation kinetics and hardening in an Al-4Cu (wt. %) alloy

Abstract

A multidisciplinary approach is presented to analyse the precipitation process in a model Al-Cu alloy.Although this topic has been extensively studied in the past, most of the investigations are focussed either on transmission electron microscopy or on thermal analysis of the processes. The information obtained from these techniques cannot, however, provide a coherent picture of all the complex transformations that take place during decomposition of supersaturated solid solution. Thermal analysis, high resolution dilatometry, (high resolution) transmission electron microscopy and density functional calculations are combined to study precipitation kinetics, interfacial energies, and the effect of second phase precipitates on the mechanical strength of the alloy. Data on both the coherent and semicoherent orientations of the ′′ / interface are reported for the first time. The combination of the different characterization and modelling techniques provides a detailed picture of the precipitation phenomena that take place during aging and of the different contributions to the strength of the alloy. This strategy can be used to analyse and design more complex alloys.

Strengthening of Al–Cu alloys by Guinier–Preston zones: Predictions from atomistic simulations

“…Metallic alloys are also strengthened by small precipitates (< 20 nm) that can be sheared by dislocations. This is the case of Guinier-Preston (GP) zones in many metallic alloys (Byrne et al, 1961;Rodríguez-Veiga et al, 2018), θ and Ω precipitates in Al-Cu and Al-Cu-Mg alloys (Nie, 2014), β 1 -MgZn 2 in Mg-Zn alloys (Wang and Stanford, 2015), β 1 in Mg-Nd alloys (Zhou et al, 2018;Huang et al, 2019), γ -Ni 3 (Al, Ti) and γ -Ni 3 Nb in Nibased superalloys. (Xiao et al, 2008;Cruzado et al, 2015), etc.…”

Multiscale modelling of precipitation hardening in Al–Cu alloys: Dislocation dynamics simulations and experimental validation

“…Afterwards, the samples were aged at 180 • C for 168 hours. The structure, size, shape and spatial distribution of the precipitates was carefully characterized by means of transmission electron microscopy (TEM) (FEI Talos) [23]. The microstructure of the aged alloys was made up of a homogeneous distribution of precipitates in the Al matrix, as shown in the high-angle annular darkfield mode (HAADF) micrographs in Fig.…”

“…1.0 ± 0.5 342 ± 47 9.0 ± 0.6 39 ± 6.6 Table 1: Volume fraction (f ), diameter (D), thickness (t) and aspect ratio (AR) of the θ precipitates in the Al-4%Cu specimens aged at 180 • C for 168 h. [23].…”

“…Taking into account the precipitate volume fraction, the remaining fraction of Cu atoms in solid solution was 3.5% of Cu. Their contribution to the CRSS was quantified by [23] and it was equal to 25 MPa.…”

“…It should be finally noted that that all the parameters that determine the interaction between the Al matrix and the precipitates were obtained from atomistic simulations or independent experimental observations and the results are free from adjustable parameters. In particular, lattice and elastic constants of the matrix and the precipitate were computed from DFT simulations [22], dislocation mobility and cross-slip parameters were obtained from MD simulations [36,39] and the solid solution contribution to the CRSS in addition to the details of the precipitate size, shape and volume fraction were taken from experimental observations [23]. Moreover, DDD simulations in combination with multiscale modelling strategies to simulate precipitate nucleation and growth during thermal treatments [52] can be used to optimize precipitate hardening of metallic alloys or design new alloys improved mechanical properties [53].…”