Enhanced tensile performance of ternary Fe-Ni-Ti peri-eutectic alloy through directional solidification associated with thermal processing

The microstructural evolution and tensile performance of ternary Fe_66.5Ni_17.6Ti_15.9 peri-eutectic alloy were studied by synergetic modulation of directional solidification and thermal processing technique. The alloy after directional solidification consisted of the vertically growing α-Fe dendrites plus interdendritic γ-Fe(Ni) + Fe₂Ti peri-eutectic. The in suit thermal processing promoted the precipitation transition of the α-Fe dendrites, and the lamellar Fe₂Ti precipitate was formed along the α-Fe grain boundaries with different orientation relationships. Compared to the conventional solidification, the synergetic modulation not only reduced the transverse grain boundaries and hindered the crack propagation, but also introduced the second phase strengthening and impeded the dislocation movement in the α-Fe dendrites. Eventually, the tensile strength and Young's modulus of this peri-eutectic alloy were enhanced by 253 % and 72 %.