Fig a shows a typical inter particle

Fig. 4(a) shows a typical inter-particle neck region. It can be clearly seen that harmine the bonding region was the result of the overlap of the TiAl+Ti3Al layers of the individual particles. The original outer periphery, seen in Fig. 3(a), composed of TiAl3, was consumed resulting in the formation of TiAl+Ti3Al. Fig. 4(b) shows three layers in the particle cross-section micrograph. The outer layer still consists of a very thin layer of TiAl3+TiAl, however, the thickness of the outer layer was lower when compared to the 6 h sintered sample (Fig. 3(c)). The second layer in Fig. 4(b) has a composition of 34%–40%Al and 60%–66%Ti making up TiAl+Ti3Al. The inner core region corresponds to the composition of intermetallic TiAl (42%–44% Al, 56%–54% Ti). Fig. 4(c) shows a high magnification micrograph of the cross-section of a sintered particle revealing bright isolated, irregular shaped regions. These regions were observed to be enriched with vanadium as indicated by EDS analysis. During reactive sintering and thermal treatment, vanadium present as solid solution in the alloy Ti–6Al–4V was observed to segregate to certain random areas within the sintered particles. This is a consequence of lower solubility of vanadium in the intermetallic phases relative to the high solubility in beta titanium at the sintering temperature. XRD analysis on these samples also reveals the presence of V–Al intermetallic (Fig. 5). Phase analysis was performed on the as-mixed powders and the sintered sample using X-ray diffraction. An XRD pattern of the powder mixture of Ti–6Al–4V and Al is presented in Fig. 5(a). It can be observed that only elemental Ti and Al peaks were present in the XRD pattern. Fig. 5(b) shows the XRD pattern of the sample sintered at 1000 °C for 24 h. XRD shows the presence of various intermetallic phases formed during reactive sintering. The final microstructure consists of TiAl along with other intermetallic phases such as Al2Ti, Al3Ti, All1V, Al8V5, and Ti3Al. The vanadium rich regions correspond to Al11V and/or Al8V5 phase in the microstructure shown in Fig. 4(c). The XRD results agree with the SEM analysis of the sintered samples. The density of the part sintered at 1000 °C for 6 h and 24 h was 3.34 g/cm3 and 3.45 g/cm3 respectively. Further detailed investigation into the phase evolution, reaction kinetics, and evaluation of mechanical properties is necessary to establish and scale up the process for mass production.
Conclusions
Introduction T-joints experience out-of-plane distortion in both longitudinal and circumferential types of welding. Many authors have studied the distortion experienced due to longitudinal welding on a plate [1–6]. The temperature field of an arc and its mechanical effect on fillet welding of plates using FEM are also reported [6] and it was found that the arc start and stop points enhance the heat input and accordingly increase distortion in the case of longitudinal welding. The out-of-plane distortion due to circumferential welding of thin-walled butt-welded pipes using FEM has been reported with the effect of weld thermal cycle on out-of-plane distortion generated under the different segment of the circumferential welding [7,8]. The buckling distortion is also another type of out-of-plane distortion experienced in case of thin cylindrical shells during circumferential welding [9,10]. Generally, out-of-plane distortion resulted in both longitudinal and circumferential fillet welding and this leads to misalignment, stress concentration, buckling and improper fit-up etc. However very few articles reported the out-of-plane distortion experienced during the circumferential welding of t-joints. The start and stop points have significant effect on out-of-plane distortion in the case of half-circumferential fillet welding in a T-joint configuration, and it has been reported that the stop points have more influence on out-of-plane distortion than the start points [11,12]. In the case of full circumferential welding, both the start and stop points merge with each other and the effect is not studied so far. It is inferred from the literature survey that transient analysis of the full circumferential multi-pass welding on a tube to pipe component in the t-joint orientation is not available either experimentally or by other modes such as FEM simulation. These data, when made available, are of vital importance for various industrial and defense applications.