Pseudobinary Phase Diagrams Of Eutectic Reaction For Pt-Containing And Pt-Free 718plus Alloys

The pseudobinary phase diagrams of Pt-containing and Pt-free 718Plus alloys are constructed to better understand how Pt affects the eutectic reaction. The phase transition temperature is obtained by differential scanning calorimetry (DSC). The compositions of gamma phase, eutectic phase, and Laves phase are obtained by energy dispersive spectrometry (EDS). Nb is set as the independent variable in the phase diagram as Nb is the most susceptible to concentration of eutectic phase during solidification. The reliability of the pseudobinary phase diagrams is verified by the results reported. According to the diagrams, on one hand, Pt increases the concentration of Nb required for the (Laves + gamma) eutectic reaction by increasing lattice space. On the other hand, the increased concentration of Nb and the slow diffusion rates of Pt and Nb cause the decrease in the temperature of the eutectic reaction. As a result, the eutectic point in the pseudobinary phase diagram moves down and shift to the right. Herein, experimental data are provided for enriching the phase diagram of 718Plus alloy.