# Fabrication and Analysis of a Ti6 Al4V Implant for Cranial Restoration
## 3 Analysis Results
Figure 13(c) illustrates the EBM test samples before and after the tensile test. The stress-strain relationship of the EBM dog bone specimens was calculated and plotted as shown in Figure 13(d). The average yield and tensile strength of the specimens were determined from the stress-strain curves. The average yield and tensile strength for the EBM specimen were found to be 825 MPa and 880 MPa respectively from the tensile test. These values were better than the average yield (795 MPa) and tensile strength (860 MPa) required for Ti6 Al4V ELI specimen [33]. Moreover, these mechanical results were similar and in accordance with the values as reported by other researchers [37,50]. The calculated yield and tensile strength in the current study were higher than the required yield and tensile strength as per the ASTM standard [33,51]. This suggested that the EBM produced cranial implant possessed the required mechanical strength that is needed in medical applications. Figure 13: Outcome from 3D comparison analysis. Similarly, the surface hardness (or the resistance to deformation) of the EBM built specimen were determined by employing Rockwell hardness test (HRC) using WOLPERT UH930 (USA) universal hardness tester (Figure S4). The Rockwell C scale is usually abbreviated HRC (Hardness Rockwell C). The indentation was generated using a cone diamond indenter with a load of 150 kgf (1.5 KN) for 3-5 s. Three arbitrary regions were identified on the top surface of three EBM built specimens and a mean value of nine measurements was computed for hardness. Each of the indentations was measured at a distance of 5 mm from the previous indentation. The surface hardness value of the Ti6 Al4V ELI specimen was in the range of 30-35 HRC (Figure 14e), which was consistent with the required ARCAM and ASTM standards [33]. Notice that the computed values of strength and hardness can further be justified through multiple studies that have investigated the mechanical properties of EBM fabricated Ti6 Al4V ELI specimen. Their studies also reported ultimate strength in the range of 775 to 1150 MPa and surface hardness in the range of 30 to 35 HRC [52; 53]. The consequent surface and elemental analysis of the EBM built specimen was also performed by employing JOEL JSM-6610 LV SEM along with the attached energy dispersive X-ray spectroscopy (EDX). The EDX analysis was conducted to analyze the material composition in Ti6 Al4V ELI post EBM fabrication. As shown in Figure 15, the Ti peak was higher than the Al and V, as anticipated. The general composition of the specimen was measured as follows: 6.24% Al. 3.89% V and 89.87% Ti in weight percent. Based on the composition results, it can be inferred that the chemical composition of the fabricated EBM specimen did not vary considerably from the initial composition of the raw material (Figure 9c). Figure 14: (**a**) EBM produced dog bone shaped specimen; (**b**) Tensile test on an Instron 2716 series machine; (**c**) EBM produced titanium tensile specimens before and after the test; (**d**) Tensile stress-strain relationship curve for test specimens and (**e**) Rockwell hardness measurement (HRC) results. To compute the weight of the substituted cranial bone, the density formulae were utilized in which volume was taken from the Magics(r) software (Materialise, Belgium). The density was assumed to be 1600 kg/m\({}^{3}\)[54]. The weights of the EBM fabricated titanium cranial implant was measured using a digital weighing scale. The results as shown in Table 2 inferred that the weight of the EBM fabricated titanium cranial implant was a closer match to the substituted defected bone portion. Hence, EBM produced titanium implant will not have any stress shielding effect on the neighboring cranial bone tissue.