Computational study of atomic mobility in hcp Mg–Al–Zn ternary alloys

Abstract

The experimental data in the literature for the hcp phase of the Mg-Al-Zn ternary system have been critically reviewed. Based on the concentration profiles from the literature, the diffusion coefficients have been re-extracted using the Hall method for the impurity diffusion, and the Sauer-Freise and the Whittle-Green strategies for interdiffusion coefficients in binary and ternary systems, respectively. Moreover, extra interdiffusion coefficients were obtained from the "Darken-type" couples, which present relative maxima or/and minima at the concentration profiles. This information was assessed to obtain an atomic mobility database, by means of DICTRA software in conjunction with the CALPHAD thermodynamic description that is able to reproduce the diffusion couple experiments. Comprehensive comparisons between the calculated results and experimental values show an excellent agreement not only for the diffusion coefficient data, but also for the concentration profiles and the diffusion paths.

High-throughput extraction of the anisotropic interdiffusion coefficients in hcp Mg–Al alloys

“…The Al impurity diffusion coefficients within the basal plane, Fig. 11a, together with the experimental impurity diffusion coefficients obtained from Mg polycrystals [13][14][15]25,40] and single crystals along the basal plane and the c axis [27]. The present results are consistent with the experimental values obtained by Brennan [15] and Kammerer [13] (a) (b) using polycrystalline Mg-Al diffusion-couples and also with the first principles calculations of Zhou [29].…”

“…11 (a) The Arrhenius expression of the Al impurity diffusion coefficient in pure Mg. The different symbols stands for experimental results in the literature for polycrystals [13][14][15]27,40] and single crystals [27]. The solid lines stand for the predicted Al impurity diffusion coefficients perpendicular to the c axis, while the dashed lines represent the predictions along the c axis.…”

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

“…It has been argued that the limited precipitation hardening of Mg-Al alloys occurs because most of the precipitates exhibit Burgers OR and lay parallel to the basal plane, and this orientation is the least efficient to block basal slip [12]. It was also suggested that the precipitate distribution is relative coarse because of the high diffusion rate of Al atoms in the Mg matrix [43]. Finally, based on the Orowan model, it was proposed that rod-shaped precipitates that grow perpendicular to the basal plane with Crawley OR ({0001} M g {111} β ; 1210 M g 112 β ) are more efficient because they intersect a larger number of basal planes for a given precipitate volume fraction [42,12,16,44].…”

Exploring the correlation between solvent diffusion and creep resistance of Mg-Ga HCP alloys from high throughput liquid-solid diffusion couple

“…The impurity diffusion of Ga in hcp-Mg is further compared in Fig. 3(b) with various alloying elements (inc. Al, Ca, Ga, Sn, Y, Mn and Zn) [6][7][8]40] with a reference to the Mg self-diffusion. Apparently, Ga is much alike Zn and diffuses faster compared to the self-diffusion of Mg, while Al is among those slower impurity diffusers like Sn and Y.…”

“…The experimental results[36] are shown as symbols and the first-principles calculations[37] are shown as solid lines for comparison. (b) Impurity diffusion coefficients of solute X (Al, Ca, Ga, Sn, Y, Mn and Zn)[6][7][8]40] are compared with reference to the Mg self-diffusion coefficient.…”