## 2 Metals Used in WDED and Types of Microstructure and Mechanical Properties
### Aluminum-Based Alloys  
The aluminum-based alloys are used in automotive [81; 82] and aerospace engineering [83] applications because they are having high corrosion resistivity and low density with a combination of mechanical and physical properties. The fabrication of the aluminum-based alloys with the WDED method needs more attention because of their different applications and very few researchers have worked on fabricating the aluminum-based alloys with the WDED. With the printing of the aluminum-based alloys in a vacuum chamber, composite materials can be achieved by using two wire printing, and the heat removal can be controlled continuously. The mechanical properties of the different aluminum-based alloys and the processing parameters and methods are shown in Table 4.  
Figure 9: The effect of the heat treatment on the microstructure of the TiAlNb alloy [74]. \begin{table}
\begin{tabular}{l l l l l l l l l l l} \hline
**Technique** & **Material** & **Process Parameters** & **Microstructure** & **Condition** & **YS (MPa)** & **UTS (MPa)** & **E1 (\%)** & **Hardness (GPa)** & **Reported by** \\ \hline  & & Vacuum chamber, Beam & & & & & & & & \\  & current: 26 to 16 mA, & & & & & & & & & \\  & & Beam acceleration & - & - & - & 105 & 289 & 21 & 1.1 & [84] \\  & & voltage: 30 kV, Wire & & & & & & & & \\  & & feeding rate & & & & & & & \\  & & 440 m/min & & & & & & & & \\  & Rotational velocity: & & & & & & & & \\  & & 2000 rpm, Traverse & & & & & & & & \\  & & velocity: 1000 mm/min, & - & - & - & - & - & - & - & - & - & - & - \\  & & Wire feeding speed: & & & & & & & & \\  & & 6000 mm/min & & & & & & & & \\  & Vacuum chamber, Beam & & & & & & & & & \\  & current: 26 to 20 u/A, & & & & & & & & \\  & & beam acceleration & - & - & - & 122.7 & 180.5 & 7.9 & 1.32 & [66] \\  & & voltage: 30 kV, Wire & & & & & & & & \\  & feeding rate & & & & & & & & \\  & & 1344 mm/min & & & & & & & & \\  & Vacuum chamber, Beam & & & & & & & & \\  & current: varied & & & & & & & & \\  & & & & & & & & & \\  & exponentially A, Beam & - & - & 2 106 (\({}^{0}\)) & 2 242 (\({}^{0}\)) & 2 24 (\({}^{0}\)) & - & - & - & - & - & - \\  & acceleration voltage: & - & - & - & 121 (\({}^{0}\)) & 253 (\({}^{0}\)) & 3 (\({}^{0}\)) & 3 (\({}^{0}\)) & - & - & - & - \\  & & 30 kV, Wire feeding rate: & & & 3: 106 (\({}^{0}\)) & 3: 210 (\({}^{0}\)) & 3: 18 (\({}^{0}\)) & - & - & - & - \\  & 1560 mm/min & & & & & & & & \\  & Vacuum chamber, Beam & & & & & & & & \\  & current: 25 mA, Beam & & & & & & & & \\  & & & & & & & & \\  & & & & & & &WDED is useful for fabricating large equipment with aluminum-based alloy with a complex shape and thin wall instead of fabricating small equipment with a simple shape because the cost of fabricating small equipment with machining is lower than the that of WDED methods. Moreover, the aluminum-based alloy fabricated by the WDED methods has lower mechanical properties as compared to the material fabricated with the machining method. [PERSON] et al. [87] investigated the microstructure of the top, middle, and bottom regions of AA5356 alloy fabricated by the EBDED method. The top region of the microstructure contains shrinkage with porosity; in addition, the shrinkage and porosities disappear at the middle stage of the sample, and the bottom region shows small porosities without shrinkage as compared to the top region [87]. [PERSON] et al. [85] fabricated AA4043 alloy with FDED, and the microstructure of the different regions is shown in Figure 10. The microstructure is uniform with the equiaxed and fined grains because of the recrystallization dynamic generated by the high strain rate and plastic deformation of the FDED process [85; 89]. As can be seen from the EBSD, the particle size of each part of the sample fabricated by the FDED decreases from the bottom to the top region of the prepared sample. This is attributed to the friction heat in the FDED method.