## 3 Results
A lamellar microstructure is more ductile than an equiaxed microstructure. The results here concluded that TA alloy would be ductile and have improved creep properties in the as-built state. To understand this microstructural transformation better, the temperature profiles of the reaction were calculated. It has already been reported that the temperature of the melt pool increased with the increase in niobium content. Using the heat equation (m\(\times\)\(\rho\)\(\times\) AT) and the data reported in Table 1, the temperatures of these \"endothermic reactions\" were calculated and reported in Table 4. Note that the specific heat of 0.61 J/g K at 25 \({}^{\circ}\)C [18] was used. Table 4 summarises that the temperature of the process increased with the addition of niobium, as anticipated from experimental observations. The binary alloy is highly exothermic; hence, it was intensely cracked [18; 19]. Ternary alloy (TA) does not have a greater loss of heat energy when compared to TB and TC. It is endothermic when compared to all other alloys. The retained energy, or minimal loss of the energy to the environment, must be the one leading to the melting and refinement of the microstructure to be fully lamellar. The reaction of Nb to Ti-Al is similar to self-propagating high-temperature synthesis reactions (SHS), which are initiated with sufficient energy being released from the reactants to the products until the reaction is completed. In a handbook of _Non-Ferrous Metal Powders_ (second edition), 2019, SHS or combustion synthesis processes, are said to have existed over three decades ago and are necessary for the preparation of intermetallics and composite materials. It was explained that the process is self-sustainable, consumes low energy, and, due to its simplicity and low cost, can be used for short production cycles. In a chapter by [PERSON] on the weldability of intermetallics in the same handbook, it was captured that while there is hot cracking and dissimilarity in microstructure between the heat affected zone and the matrix that reduces the mechanical strength of the weld, with solid-state welding (SHS process), such defects can be avoided [20]. The temperature calculations in Table 4 can be read in association with the dissolved aluminium in the alloy (Table 3). It appears that the least exothermic reaction (towards endothermic) leads to the least amount of aluminium being retained in the alloy. This is a consistent observation in the additive manufacturing of Ti-Al alloys. AM processes that are sustained with high energy (in our case, retained heat) lead to the vaporisation of aluminium in the \(\gamma+\alpha_{2}\) phase alloys. The results of aluminium dissolution and self-heat generation during alloying Nb to Ti48 Al (at. %) alloy are summarised in Figure 6, where it is seen that niobium solubility leads to a high melt-pool temperature and a decrease in aluminium solubility. \begin{table}
\begin{tabular}{c c c c} \hline
**Alloy** & **Nb (at. \%)** & **Temperature (\({}^{\circ}\)C)** & **Microstructure** \\ \hline BA & 0 & \(-253\) & (\(\alpha_{2}+\gamma\)) thick laths of \(\alpha_{2}\) lamellar \\ TC & 6 & \(-211\) & \(\alpha_{2}\) laths \(\rightarrow\)\(\beta\)-precipitates \\ TB & 8 & \(-209\) & \(\alpha_{2}\) laths \(\rightarrow\)\(\alpha_{2}+\gamma\) grain lamellae \\ TA & 10 & \(-192\) & \(\alpha_{2}\) laths \(\rightarrow\) refined lamellar \\ \hline \end{tabular}
\end{table} 
Table 4: Temperature values. After conducting the above experiments, it was pertinent to delve deeper into the findings using the numerical modelling approach. Tlotleng, 2019 Tlotleng, 2019 Tlotleng, 2019 [PERSON] et al., 2016 [PERSON] et al. (2016) stated that a single deposited unit length of printed product, subjected to laser power, experiences melting and solidification twice during printing.