## 3 Results
### Microstructure of Zn1.5 Mg Solder  
The microstructure of the Zn1.5 Mg type soldering alloy, Figure 9, is formed of a zinc matrix. Segregation of binary eutectics in the form of lamellas occurred on the boundaries of Zn grains.  
The chemical composition of specific zones within the soldering alloy was identified via the utilization of EDX analysis. The designated measurement points, depicted in Figure 10, are annotated with numerical values ranging from 1 to 8. The results of EDX analysis are shown in Table 5.  
Figure 8: Equilibrium binary diagram of the Mg-Zn system [22].  
Figure 9: Microstructure of Zn1.5 Mg solder from SEM (BEI) in the condition after etching, (a) magnification \(500\times\), (b) magnification \(1000\times\).  
In Spectrum 1 and 2 measurement points, small, rarely occurring constituents were observed, unanimously corresponding to the stochiometric formula of intermetallic compound type MgZn\({}_{2}\). They were formed by the periteectic reaction at the temperature of 381 \({}^{\circ}\)C, in accordance with the Mg-Zn phase diagram shown in Figure 8. The Spectrum 3 and 4 measurement points showed primarily solidified large grains of pure zinc.  
In the Spectrum 5 to 7 measurement points, the binary eutectics formed by the eutectic reaction at 364 \({}^{\circ}\)C were proven. It was comprised of pure zinc lamellas and an intermetallic compound of the type Mg\({}_{2}\)Zn\({}_{11}\).  
The Spectrum 8 measurement point identified small dark spots in the structure, corresponding to zinc oxide.  
Even though the nominal composition of soldering alloy with 1.5 wt. % Mg, i.e., 4 at. % Mg, in accordance with the phase diagram, occurs on the right of the eutectic point (92.2 at. % Zn, 364 \({}^{\circ}\)C)-(Figure 8), formation of small islands of the MgZn\({}_{2}\) phase took place, apparently during magnesium dissolution in the Zn melt. However, the constituents of this kind occurred relatively scarcely in the structure.  
The XRD analysis of Zn1.5 Mg solder, similar to the EDX analysis, verified the existence of a solid solution comprising zinc (Zn) and an intermetallic magnesium phase, specifically MgZn\({}_{2}\). The detection of a fine Mg\({}_{2}\)Zn\({}_{11}\) phase was not observed in the XRD analysis. The findings from the diffraction analysis are illustrated in Figure 11.  
Figure 10: Point EDX analysis of Zn1.5 Mg solder.  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Spectrum** & **Mg [at. \%]** & **Zn [at. \%]** & **O [at. \%]** & **Solder Component** \\ \hline Spectrum 1 & 32.5 & 67.5 & - & phase MgZn\({}_{2}\) \\ Spectrum 2 & 32.7 & 67.3 & - & phase MgZn\({}_{2}\) \\ Spectrum 3 & - & 100 & - & matrix Zn \\ Spectrum 4 & - & 100 & - & matrix Zn \\ Spectrum 5 & 9.6 & 90.4 & - & eutectic compound (Zn) + Mg\({}_{2}\)Zn\({}_{11}\) \\ Spectrum 6 & 10.5 & 89.5 & - & eutectic compound (Zn) + Mg\({}_{2}\)Zn\({}_{11}\) \\ Spectrum 7 & 9.8 & 90.2 & - & eutectic compound (Zn) + Mg\({}_{2}\)Zn\({}_{11}\) \\ Spectrum 8 & - & 93.4 & 6.6 & Zn oxides ZnO \\ \hline \end{tabular}
\end{table}
Table 5: Results of point EDX analysis of Zn1.5 Mg solder.  
The planar distribution of the magnesium phase in the eutectic zinc matrix is documented in Figure 12. On the grain boundaries of the Zn matrix, segregation of binary eutetectics (Zn) + Mg\({}_{2}\)Zn\({}_{11}\) in the form of lamellas took place.