Basal dislocation/precipitate interactions in Mg–Al alloys: an atomistic investigation

Abstract

The interaction between edge basal dislocations and β-Mg 17 Al 12 precipitates was studied using atomistic simulations. A strategy was developed to insert a lozenge-shaped Mg 17 Al 12 precipitate with Burgers orientation relationship within the Mg matrix in an atomistic model ensuring that the matrix/precipitate interfaces were close to minimum energy configurations. It was found that the dislocation bypassed the precipitate by the formation of an Orowan loop, that entered the precipitate. Within the precipitate, the dislocation was not able to progress further until more dislocations overcome the precipitate and push the initial loop to shear the precipitate along the (110) plane, parallel to the basal plane of Mg. This process was eventually repeated as more dislocations overcome the precipitate and this mechanism of dislocation/precipitate interaction was in agreement with experimental observations. Moreover, the initial resolved shear stress to bypass the precipitate was in agreement with the predictions of the Bacon-Kocks-Scattergood model.

Interactions between basal dislocations and β1′ precipitates in Mg–4Zn alloy: Mechanisms and strengthening

“…Mg-RE alloy showed that basal dislocations have to pile-up at precipitate/matrix interface before they were able to shear the precipitate. These results are in agreement with recent molecular dynamics simulations by Esteban-Manzanares et al [47] which showed that the first dislocation entered the precipitate but was not able to progress further, leading to the formation in Mg and they rapidly form loops around the precipitates. Experimental evidence [48] showed that sometimes the dislocations were attracted by the precipitate/matrix interface and preferred to glide along the interface rather than shear the precipitate and similar observations were provided by molecular dynamics simulations [47].…”

“…These results are in agreement with recent molecular dynamics simulations by Esteban-Manzanares et al [47] which showed that the first dislocation entered the precipitate but was not able to progress further, leading to the formation in Mg and they rapidly form loops around the precipitates. Experimental evidence [48] showed that sometimes the dislocations were attracted by the precipitate/matrix interface and preferred to glide along the interface rather than shear the precipitate and similar observations were provided by molecular dynamics simulations [47]. It should be noticed that first principles calculations of the generalized stacking fault energy have shown that high shear stresses are necessary to promote dislocation slip in these intermetallic phases [49] and, thus, several dislocations have to pile-up before the Orowan loop can penetrate and collapse within the precipitate.…”

“…5. The accumulation of dislocations led to the shearing of the precipitates by the basal dislocations, in agreement with the atomistic simulations [47].…”

Density functional simulations of pressurized Mg-Zn and Al-Zn alloys

“…14,[18][19][20][21] Prominent examples can be found in aluminium alloys that play increasingly crucial roles in various industrial products. 5,[8][9][10][11][12][22][23][24][25] One of the main goals of alloying matrices is to obtain the most lightweight and high-strength alloys that can be extensively used in aircraft industries, modern trains and vehicles, and so forth. The central mechanisms for enhancing the strength of aluminium is to produce uniform distributions of nucleated precipitates and solid microstructures in the aluminium matrix with different solute elements such as Zn, Mg, Si, Cu, Mn, and Cr.…”

Atomistic modeling of the strengthening mechanisms in FCC and HCP metals

“…Thus, the details of the dislocation/precipitate interaction in these alloys as well as the strengthening provided are not well known. Consequently, MS and MD were carried out to assess the interaction between basal dislocations and β-Mg 17 Al 12 precipitates in Mg-Al alloys (Esteban-Manzanares et al, 2019b). Dickel et al (2018), which stand for 2NN-MEAM potentials.…”