## 3 Machinability of AM Ti6 Al4V Alloy  
Machinability is assessed based on factors such as tool wear, tool life, chip formation, cutting forces, temperature fields, burr size, and surface quality. To enhance productivity, tungsten carbide (WC) inserts, whether coated or uncoated, are commonly used for machining titanium alloys. Wet cutting environments help control heat generation and accumulation at the tool-workpiece interface, while dry cutting results in a cleaner working environment. In wet cutting conditions, lower temperatures at the cutting tip lead to reduced cutting forces. Additionally, a significant challenge in machining Ti6 Al4V alloy is its chemical reactivity with the tool material, which can result in rapid tool wear due to either dissolution of the tool material or chemical reactions with the chip [38]. Ti6 Al4V alloy's machinability depends on cutting force, tool life, missing temperature, burr size, chip formation, and surface integrity [39; 40]. The elasticity of a material contributes a significant portion to determining its machinability [41].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Reference**} & **Machining** & \multirow{2}{*}{**Machining Parameters**} & **AM** & **Cutting** & \multirow{2}{*}{**Machining Responses**} \\  & & & **Techniques** & **Environment** & \\ \hline \multirow{8}{*}{[36]} & & \multicolumn{2}{c}{Milling parameters} & & & \\  & & V = 80 m/min & & & \\  & & f = 0.06 mm/rev & & & \\  & & d = 30 mm (axial) and & & & Surface roughness, \\  & Drilling and & 1.0 mm (radial) & WAAM & Dry & cutting forces, and tool wear \\  & milling & Drilling parameters & & & \\  & & V = 9.0 m/min & & & \\  & & f = 0.09 mm/rev & & & \\  & & hole depth = 12.5 mm & & & \\  & Up-milling, & V = 50, and 60 m/min & & & \\
[6] & \
\begin{tabular}{c} Up-milling, \\ down- \\ milling, and \\ slot-milling \\ \end{tabular} &
\begin{tabular}{c} V = 50, and 60 m/min \\ f = 0.12 mm/rev \\ d = 0.4 mm (axial) \\ \end{tabular} & WAAM (PAL) & Dry & Surface roughness \\  & & F =100 mm/min & & & \\
[37] & LAM-Milling &
\begin{tabular}{c} G = -0.3 mm \\ Spindle speed (N) = 6000 rpm \\ Preheating temp—600 \({}^{\circ}\)C \\ V = 70 m/min \\ d = 1.25 mm \\ f = 0.15 mm/rev \\ N = 4000 rpm \\ d = 0.6 mm \\ f = 0.05–0.13 mm/tooth \\ \end{tabular} & DED & Dry & Surface roughness \\  & & DDD & Dry & Surface roughness \\  & & DDD & Dry & Surface roughness \\  & & f = 0.15 mm/rev & & \\  & & & Tool flank wear, \\  & & d = 0.6 mm \\  & & & water & subsurface deformation \\ \hline \hline \end{tabular}
\end{table}
Table 1: _Cont._  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Process**} & **Yield Strength** & **Ultimate Tensile** & **Percentage** \\  & **(MPa)** & **Strength (MPa)** & **Elongation (\%)** \\ \hline ASTM Standard & 827 & 896 & 10 \\ As deposited & 1105 + 19 & 1165 + 22 & 4 + 1 \\ Air-cooled at 950 \({}^{\circ}\)C & 975 + 15 & 1053 + 18 & 7.5 + 1 \\ The furnace cooled at 950 \({}^{\circ}\)C & 959 + 12 & 1045 + 16 & 10.5 + 1 \\ Air-cooled at 1050 \({}^{\circ}\)C & 931 + 16 & 1002 + 19 & 6.5 + 1 \\ The furnace cooled at 1050 \({}^{\circ}\)C & 900 + 14 & 951 + 15 & 7.5 + 1 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Mechanical properties of titanium alloy parts manufactured by DMD as built and heat-treated [7].