Eutectic Growth Suppression for Cooperative Strengthening and Anticorrosion of Ni–Fe–Cr–Si Alloy

The competitive growth between primary phase and eutectic, correlated strengthening and corrosion mechanism of Ni50Fe20Cr20Si10 alloy is investigated by electromagnetic levitation technique. The surface tension of the molten alloy increases from 1.69 to 1.81 N m−1 with undercooling, resulting in the increment of the alloy's sphericity from 0.83 to 0.89. The augmentation in undercooling enhances the nucleation rate and growth velocity of the γ phase and impedes the formation of Ni3Si, tending to the single‐phase (γ) microstructure at 205 K undercooling. Moreover, the γ phase transforms from weakly textured coarse dendrites into randomly distributed refined equiaxed grains as the undercooling increases. The grain refinement mechanism changes from dendrite fragment caused by electromagnetic stirring to stress‐induced recrystallization with an increase in undercooling. In this condition, the alloy with 205 K undercooling exhibits 13.2% increase in yield strength compared with the master alloy. Quantitative analysis of strengthening mechanism shows that this improvement was mainly attributed to grain boundary strengthening and twin boundary strengthening. Furthermore, compared with master alloy, the anticorrosive property of 205 K undercooled alloy is significantly enhanced with higher corrosion potential of −0.247 VSCE and lower corrosion current density of 8.3 × 10−5 A cm−2 in sulfuric acid solution.