## 2 Materials and Methods
### Testing of AZ91/x-\(Si_{3}N_{4}\) Composites
#### 2.2.2 Mechanical Properties  
Hardness is a material property that measures resistance to indentation or scratches. Determining the hardness of a material is significant because it is associated with other properties such as strength. In this study, the hardness test as per ASTM E10 standard method [30] was performed using a Brinell hardness testing machine, and five indentations were made on each sample. The average of all five readings was considered for the analysis, with the hardness value reported as the Brinell Hardness Number (BHN).  
Strength is a crucial property of structural materials and plays a significant role in understanding the behavior of composite materials. In this study, the strength of the fabricated composites was investigated using a universal testing machine. Tensile strength according to ASTM E8 [31] as shown in Figure 5a, compressive strength as per ASTM E9 method [32] as shown in Figure 5b, and elongation were measured. For both tensile and compressive tests, three samples were taken for each combination. The samples used for the tensile test before and after the test are depicted in Figures 6 and 7, respectively, while Figure 8 illustrates the samples used for the compressive test as well as the samples after the test. These tests provide valuable insights into the mechanical properties and performance of the fabricated composite materials.  
Figure 5: (a) Tensile testing (ASTM E8) and (b) compression and forgeability testing (ASTM E9).  
Figure 6: (**a–f**) Tensile test samples (before test).  
Figure 7: Tensile test samples (after test).  
The Izod impact strength test was conducted on the metallic material specimens according to ASTM E-23 standards [33]. The specimens were prepared accordingly. The test was performed using an impact testing machine equipped with a pendulum hammer weighing 300 N. Three readings were taken for each specimen, and the average of these readings was used for the analysis. Table 4 provides detailed information about the Izod test, including specific parameters and measurements.  
The flexural strength, also known as the bending strength, was determined using a three-point flexural test. This test method is illustrated in a block diagram, shown in Figure 9. The test specimens used had a rectangular cross-section. Three samples of each combination were tested, and the average of the readings obtained was considered for further analysis and examination of the flexural strength properties. The flexural strength was calculated using the general formula expressed in Equation (3).  
\[\text{Flexural strength},\ \sigma\ =\frac{3 FL}{2 bd^{2}} \tag{3}\]  
where \(F\) = applied force, \(L\) = length of support, \(b\) = width of the specimen, and \(d\) = thickness of the specimen.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**S.No** & **Izod Impact Strength Test** \\ \hline
1 & Materials tested & AZ91/x-Si\({}_{3}\)N\({}_{4}\) composites \\
2 & Position of specimen & Vertical \\
3 & Notch type & V-shape (45\({}^{\circ}\)) \\
4 & Notch face direction & In front of striker \\
5 & Type of striker & Farming hammer \\
6 & Striking point & Upper tip of specimen \\
7 & Specim size & 75 mm \(\times\) 10 mm \(\times\) 10 mm \\ \hline \hline \end{tabular}
\end{table}
Table 4: Izod impact strength test details.  
Figure 8: Compression test samples (**a**) before testing and (**b**) after testing.  
Figure 9: Three points flexural strength test of AZ91/x-Si\({}_{3}\)N\({}_{4}\) composites.  
Forgeability, which measures the change in height compared to the original height during compression, was evaluated in this study. The forgeability test was performed using a hydraulic pallet press machine. Three samples were tested for each combination of composites, and the average value was calculated for analysis purposes.