# Rare Earth Magnet Recycling and Materialization for a Circular Economy--A Korean Perspective
## 6 Materialization  
Due to the wide range of applications of Mg in the automobile and aerospace industries, it is crucial to enhance the properties of Mg alloys, especially for high-temperature applications. Several studies have investigated the replacement of conventional Mg-based alloys such as Mg-Al with Mg-RE, as the latter has significantly improved properties. The addition of REEs to Mg results in improvements in the mechanical strength, biocompatibility, corrosion resistance, bioactivity, and other properties [48]. Similarly, the addition of Nd to Mg improves the hardening and strength of Mg after thermal treatment [49].  
For example, in biodegradable biomedical magnesium alloy (Mg-Nd-Zn-Zr), Nd is used as the main alloying element. Nd is preferred because of its high strength and because when it is added it forms an intermetallic phase (Mg12 Nd) with Mg, which acts as an obstacle to dislocation movement at elevated temperatures and causes precipitation strengthening. It has also been reported that Nd does not exhibit any toxicity. As Mg-Nd already has a significant strengthening effect, the further addition of a small amount of Zn can increase the ductility and deformability of the alloy [50].  
Additionally, Mg-Nd from LME can be directly used as a raw material in making QE22 (Mg-2 Ag-2 Nd-0.5 Zr; Ag = silver and Zr = zirconium) alloy. The same is true for WE54 (Mg-5Y-3 RE-(1.5-2 Nd)-0.5 Zr; Y = yttrium) and NZ30K (Mg-3.0 Nd-0.2 Zn-0.5 Zr; Zn = zinc) Mg alloys. These two alloys show improved tensile properties and creep resistance at both normal and high temperatures [51].  
Similarly, in the making of the Mg-2.0 Zn-1.0 Mn (ZM21) alloy, Nd was added in the form of the master alloy Mg-Nd (20 wt. %), which can be achieved from the LME process. Certain amounts of Ce and Nd were added to enhance the mechanical and other properties of the alloy. In this ZM21 alloy, the average grain sizes with the addition of 0.4 wt.% Nd and Ce reached 6 \(\pm\) 3 mm and 13 \(\pm\) 2 mm, respectively. The resulting changes of mechanical properties were mainly attributed to a reduction in the basal texture intensity and refinement of the grain size, dispersion density, and distribution position of fine second-phase particles [51]. Moreover, Mg-Nd from our recycling process has been used as a master alloy to make other alloys, e.g., the addition of 2.5% yttrium to Mg-3%Nd showed significant improvements in the tensile strength, fatigue strength, and creep resistance. This alloy is utilized in automobiles and helicopters [52; 53; 54]. Furthermore, the addition of 0.2 wt.% Zn and 0.4 wt.% Zr to Mg-3 wt.%Nd alloy (Mg-Nd-Zn-Zr alloy) resulted in an alloy with increased hardening, as Zr worked as a grain refiner [54].  
It can be seen that Mg-Nd alloy is employed for various applications, while research into additional applications is also underway. The Mg-Nd alloy achieved from the LME process can either be used directly as an input for the materialization of the abovementioned alloys, or Nd can be separated by VD and applied for magnet manufacturing. This process can be extended to Mg-Dy alloy as well, which is one of the future prospects for the ReMaT process.