*Article* **An Effective Strategy to Maintain the CALPHAD Atomic Mobility Database of Multicomponent Systems and Its Application to Hcp Mg–Al–Zn–Sn Alloys**

**Ting Cheng, Jing Zhong and Lijun Zhang \***

State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China; chengting@csu.edu.cn (T.C.); zhongjingjogy@csu.edu.cn (J.Z.) **\*** Correspondence: lijun.zhang@csu.edu.cn

**Abstract:** In this paper, a general and effective strategy was first developed to maintain the CALPHAD atomic mobility database of multicomponent systems, based on the pragmatic numerical method and freely accessible HitDIC software, and then applied to update the atomic mobility descriptions of the hcp Mg–Al–Zn, Mg–Al–Sn, and Mg–Al–Zn–Sn systems. A set of the self-consistent atomic mobility database of the hcp Mg–Al–Zn–Sn system was established following the new strategy presented. A comprehensive comparison between the model-predicted composition–distance profiles/interdiffusivities in the hcp Mg–Al–Zn, Mg–Al–Sn, and Mg–Al–Zn–Sn systems from the presently updated atomic mobilities and those from the previous ones that used the traditional method indicated that significant improvement can be achieved utilizing the new strategy, especially in the cases with sufficient experimental composition–distance profiles and/or in higher-order systems. Furthermore, it is anticipated that the proposed strategy can serve as a standard for maintaining the CALPHAD atomic mobility database in different multicomponent systems.

**Keywords:** atomic mobility; CALPHAD; diffusion couple; HitDIC; Hcp Mg–Al–Zn–Sn alloys
