# Evaluating the Degradation of WE43 for Implant Applications: Optical and Mechanical Insights
## 4 Results and Discussion  
### Initial State  
Prior to commencing the experiments in HBSS, an analysis of the initial state was required. For this purpose, the surface of sample geometry 1 (Figure 7a-c) and 2 (Figure 7d-f) were examined with the confocal LED microscope and the 3D profilometer. In Figure 7a), the height deviation from the set base plane is visible on the 3D profilometer for sample geometry 1. It is evident that the sample does not show any major deviations from the surface baseline. Only a slight shift in the height of the sample is visible. This is important for the investigations in the HBSS with regard to the subsequent comparison of the height development after degradation. Furthermore, the overview image of the sample can be observed in Figure 7b. In this image, slight grooves caused by the manufacturing process and post-processing can be detected. These details are more clearly in the image captured using the confocal LED microscope (Figure 7c). Small inclusions are also visible in the microscope image, which could represent alloy precipitates. The surface roughness was measured, resulting in an R\({}_{\mathrm{z}}\) value of 2.55 \(\upmu\)m (\(\pm\)0.45).  
The investigation results for sample geometry 2 are depicted in Figure 7d-f. These findings align with those of sample geometry 1, as anticipated. Similar to sample geometry 1, small inclusions are identifiable in the microscope images. Moreover, a comparable R\({}_{\mathrm{z}}\) value of 2.55 \(\upmu\)m (\(\pm\)0.65) was determined.  
The results of [PERSON]'s modulus and hardness mappings from the centre of the planar sample surface (a,c; MP 2) and the centre side (b,d; MP 1) are presented in Figure 8 for sample geometry 1 as an example. When comparing the results from [PERSON]'s modulus, no difference between the two test areas could be identified (Figure 8a,b). The average  
Figure 7: Exemplary result of the optical measurement from the initial state of sample geometry 1 (**a–c**) and sample geometry 2 (**d–f**).  
[PERSON]'s modulus is about 45 GPa. In some areas, a maximum of about 80 GPa is measured. The individual higher values may be due to intermetallic compounds containing yttrium or neodymium from the alloy. Mapping from the side region shows a blue area with very low values (Figure 8b). This area represents the embedding material. A similar distribution of the maximum and minimum values within the hardness mapping of the two investigated areas is evident (Figure 8c,d). On average, a hardness of approximately 1.125 GPa was recorded. Maximum and minimum values of 3.0 GPa and 0.75 GPa, respectively, were measured.  
In the etched (1% alcoholic nitric acid) metallographic images (Figure 8e,f), no difference can be seen between the edge centre and the centre side of the sample. Uneven grain sizes can be recognised in both areas. It can be assumed that the dark particles in the metallographic images are inclusions or precipitates of the alloy, which were measured as hard particles in the hardness and [PERSON]'s modulus mappings. The grain size is between a few micrometres and 25 \(\upmu\)m in individual cases.  
Figure 8: Exemplary comparison of [PERSON]’s modulus and hardness measurements at two positions (centre of the surface (**a,c**) MP 2 and centre side of the sample (**b,d**) MP 1), etched metallographic images (**e,f**) of the sample geometry 1.