## 3 Results  
Figure 3 presents the microstructure of the as-built and heat-treated binary Ti-Al alloy. The elemental analyses of the as-built (or produced) alloy and subsequent heat treatments (1200 \({}^{\circ}\)C and 1400 \({}^{\circ}\)C) concluded that the as-built binary Ti-Al alloy contained 76 (at. %) Ti and 24 (at. %) Al. After heat treatment at 1200 \({}^{\circ}\)C, aluminium increased to 49 (at. %), while Ti decreased to 51 (at. %). There was no significant change in chemistry when the sample was heat treated to 1400 \({}^{\circ}\)C, since 52 (at. %) Ti and 48 (at. %) Al were reported. The difference in the chemistry between the as-built and heat-treated samples was attributed to the dissolution of the free aluminium, which tends to bubble out of melt-pool solution, and its segregation during laser in situ alloy synthesis. The segregated aluminium can be said to be the cloud or white and bright material/phase that sits on the matrix of the alloy and is wrapped as a filler in the formed solidification cracks, as seen from Figure 3a. Post-heat treatment led to an equiaxed lamellae microstructure (Figure 3c) and a duplex \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample ID** & **Temperature (\({}^{\circ}\)C)** & **Holding Time (min)** & **Method of Cooling** \\ \hline As-built & 25 & None & None \\ HT 1 & 1200 & 120 & Furnace cooling \\ HT 2 & 1400 & 120 & Furnace cooling \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Heat treatment conditions. Figure 3: LENS synthesised Ti–Al: as-built (**a**), HT 1200 \({}^{\circ}\)C (**b**), and HT 1400 \({}^{\circ}\)C (**c**). phase microstructure (Figure 3b) being formed. These microstructures are further discussed in the latter sections of this paper under anneal conditions. These microstructures have limited engineering applications. To improve their odds of having industrial applications, researchers' micro-alloy the stable binary \(\gamma\)-TiAl with stabilising metals such as chromium (Cr) and niobium (Nb). Herein, ternary alloys containing Nb were fabricated and are reported in Figure 4.  
Figure 4 shows printed cubes that look different considering their surface texture. The surface texture or finish of the ternary cubes looks smooth to rough, but not as rough as the surface of the binary Ti-Al alloy. The surface smoothness was observed to increase with the increase in niobium feed rate (rpm), as seen with cube 1 (which corresponds to 1.0 rpm), cube 2 (which corresponds to 1.6 rpm), and cube 3 (which corresponds to 2.0 rpm), respectively. More importantly, as opposed to the binary alloy, the ternary cubes were produced with no obvious surface cracks. It was anticipated from working with the binary alloy (Ti-Al) that the ternary alloys would have massive surface cracks or even delaminate. Intense cracking is attributed mainly to rapid melt-pool heating and cooling rates during printing or the inherent residual stresses and brittle nature of aluminides. The absence of surface cracks in the ternary builds could not be explained immediately. [PERSON] et al. (2018) studied the laser surface melting of \(\gamma\)-TiAl alloy, both experimentally and numerically, by varying the laser power. They observed micro-cracking in the melted region of the built, which was due to rapid cooling rates, and concluded that these high cooling rates led to refined microstructures. [PERSON] et al. (2019) reported a curve showing the cracking frequency with an increase in energy input and concluded that cracks decreased with the increase in energy input. During LENS printing of the ternary cubes (being studied here), the brightness and glow of the melt pool were seen to increase with the increase in the niobium content. Intuitively, this meant that the melt-pool thermal heat, or temperature, was increasing with an increase in niobium content.