## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Specimens** & **O (wt.\%)** & **C (wt.\%)** & **N** & **Density** & **Yield Stress** & **UTS** & **Elongation** \\  & & & **(wt.\%)** & **(g/cm\({}^{3}\))** & **(MPa)** & **(MPa)** & **(MPa)** & **(\%)** \\ \hline B-1200 \({}^{\circ}\)C-180 min & 0.318 & 0.071 & 0.028 & 4.26 & 810 & 927 & 4.6 \\ B-1300 \({}^{\circ}\)C-120 min & 0.326 & 0.077 & 0.031 & 4.26 & 790 & 900 & 3.9 \\ P-1200 \({}^{\circ}\)C-180 min & 0.250 & 0.076 & 0.034 & 4.26 & 818 & 928 & 5.2 \\ P-1300 \({}^{\circ}\)C-120 min & 0.312 & 0.070 & 0.034 & 4.28 & 800 & 913 & 5.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Impurity content, density, and mechanical properties of the sintered specimens. Figure 6: The **(a)** green and **(b)** as-sintered “dog-bone” tensile bars. Figure 7: Stress-strain curves of **(a)** B samples sintered at 1200 \({}^{\circ}\)C for 180 min, **(b)** B samples sintered at 1300 \({}^{\circ}\)C for 120 min, (c) P samples sintered at 1200 \({}^{\circ}\)C for 180 min, and (d) P samples sintered at 1300 \({}^{\circ}\)C for 120 min. Figure 9 shows the optical micrographs of B and P samples sintered at 1200 \({}^{\circ}\)C for 180 min, (**b**) B sample sintered at 1300 \({}^{\circ}\)C for 120 min, (**c**) P sample sintered at 1200 \({}^{\circ}\)C for 180 min, and (**d**) P sample sintered at 1300 \({}^{\circ}\)C for 120 min. Figure 8: SEM images of the fracture surfaces of (**a**) B sample sintered at 1200 \({}^{\circ}\)C for 180 min, (**b**) B sample sintered at 1300 \({}^{\circ}\)C for 120 min, (**c**) P sample sintered at 1200 \({}^{\circ}\)C for 180 min, and (**d**) P sample sintered at 1300 \({}^{\circ}\)C for 120 min. Figure 9: Optical micrographs of (**a**) B sample sintered at 1200 \({}^{\circ}\)C for 180 min, (**b**) B sample sintered at 1300 \({}^{\circ}\)C for 120 min, (**c**) P sample sintered at 1200 \({}^{\circ}\)C for 180 min, and (**d**) P sample sintered at 1300 \({}^{\circ}\)C for 120 min. The oxygen level of the B samples sintered at 1200 \({}^{\circ}\)C is slightly higher than 0.3 wt%, and its elongation is 4.6%. Both the chemical compositions and mechanical properties cannot meet the aerospace industry standard, which requires the oxygen level for Ti-6 Al-4V not exceeding 0.2 wt%. However, the requirements for non-aerospace applications are less stringent [28]. Therefore, we expect that the high strength and acceptable ductility of the MIMed Ti-6 Al-4V are still sufficient for many engineering applications. After the processing parameters are optimized, a batch of real industrial Ti-6 Al-4V parts can be fabricated by MIM successfully. Figure 10 shows a watch case fabricated by the MIM process from the presented blended powder. Sintered to a density of 4.26 g/cm\({}^{3}\), the watch case weighs ~6 g and has a curved surface and internal complex structures. All the complex structures are net shape formed without machining. It is both difficult and expensive for other processing methods, such as forging or casting, to mass produce watch cases. To avoid defects during injection molding, mold flow software was used to determine the suitable injection molding parameters and optimize the gate positions. The debinding and sintering processes are carefully designed to prevent the dimensional distortion. Tolerances controlled within \(\pm\)0.5% of the nominal dimensions can be consistently achieved.