# In Vitro Corrosion Behavior of Zn3 Mg0.7Y Biodegradable Alloy in Simulated Body Fluid (SBF)
## 3 Results
### Microhardness and Microscratch Behavior of the Experimental Materials  
The influence of the addition of Mg and Y elements on mechanical properties was obvious, first of all based on the differences between the indentor microhardness test traces, as shown in Figure 4a-d. The traces decreased in dimensions from Zn to ZnMg, and Zn3 Mg0.7Y, based on the superior hardness of the compounds, formed between ZnMg and ZnY, while it did not form for pure Zn. The dimensional difference between the traces from Figure 4b,c was shown by the MgZn compounds (MgZn2, MgZn11) caught during the second test on the Zn3 Mg alloy and explains the differences between the microhardness results in Table 2 (points 1 and 4). Figure 4: Optical microscopy of indented areas: (**a**) Zn; (**b**) and (**c**) ZnMg; (**d**) Zn3 Mg0.7Y. Figure 3: (**a**) Elemental mapping of all components; (**b**) Zn element; (**c**) Mg element; (**d**) Y element; (**e**) XRD spectrum of Zn3 Mg0.7Y. The formation of ZnMg and ZnY compounds improved the microhardness of the pure Zn by more than two-fold. The contribution of Y and especially the YZn compounds was the increase in the microhardness of the material. Except two areas--probably with a lower content of ZnMg and ZnY compounds, points 1 and 4--all the results for Zn3 Mg0.7Y material presented a higher hardness compared to the Zn3 Mg alloy. [PERSON] et al. [27] obtained (microalloyed with Al, Mn, Cu and Ag) a Vickers hardness of 51 \(\pm\) 3.4 HV for Zn, and after alloying with Li, a value of 90 \(\pm\) 6.9 HV. [PERSON] et al. [28] also present an increase in the Vickers hardness of pure zinc with the addition of Ca and Cu from 32.12 HV to 71.83 HV Zn-1 Ca-0.5 Cu. [PERSON] obtain the following values of microhardness: 93.71 HV for the Zn-1 Mg-0.1 Sr alloy, and 109.34 HV for the Zn-1 Mg-0.5 Sr alloy, which are higher than those of pure Zn, suggesting the effectiveness of alloying in improving its mechanical property [29]. [PERSON] et al. present Vickers hardness values for samples Zn0.5 Mg, Zn1 Mg and Zn1.5 Mg after a hot extrusion process: 75 HV, 95 HV and 115 HV, respectively [30; 31]. The scratch test is regularly used for the assessment of the cohesive and adhesive strength of thin films and coatings. By default, its evaluation is based on the analysis of the depth-load-time record and the microscopic observation of residual scratch grooves [32]. In our case, we tested the materials in order to compare their behavior for similar reasons. In Figure 5, the scratch behavior of the samples is presented for Figure 5a F\({}_{\mathrm{x}}\) vs. Y (mm), Figure 5b COF vs. Y (mm) and Figure 5c AE vs. Y (mm). The quantitative results are given in Table 3. Both the force F and friction coefficient COF presented similar behaviors with higher values for pure Zn and similar variations for Zn3 Mg and Zn3 Mg0.7Y. Based on the behavior of pure Zn, the increase in F\({}_{\mathrm{x}}\) and COF values can be attributed to overlapping of the soft Zn matrix, especially on the first 4 \(\upmu\)m of the scratch. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Material** & **Pure Zn** & **Zn3 Mg** & **Zn3 Mg0.7Y** \\  & **(HV)** & **(HV)** & **(HV)** \\ \hline Point 1 & 45.1 & 118.0 & 118.6 \\ Point 2 & 50.7 & 121.0 & 126.7 \\ Point 3 & 51.0 & 129.3 & 133.8 \\ Point 4 & 48.0 & 127.0 & 120.1 \\ Point 5 & 62.5 & 125.7 & 132.4 \\ \hline Average & 51.5 & 124.2 & 126.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Vickers microhardness values on cast samples. Figure 5: _Cont_. The visual analysis of the residual groove provides the most detailed description of the final damage of the surface (crack patterns, extent of plastic deformation, delamination, etc. ), but it may be a time-consuming approach. Although the continuous recording of indenter penetration depth and applied load offers instantaneous information about the performance of the tested material, it may not provide a sufficient description of the sample's deformation behavior [33].