Enhancing the Corrosion Resistance of Near-Stoichiometric Ni4Mo Alloy by Doping with Yttrium

Abstract

It is shown that doping with yttrium can significantly improve the corrosion resistance of near-stoichiometric Ni 4 Mo alloy, which is otherwise susceptible to severe intergranular attack in the ordered condition. A oneto-one correspondence is found to exist between corrosion resistance and morphology of ordered Ni 4 Mo. The susceptibility to intergranular corrosion is correlated with a discontinuous grain boundary reaction resulting from selfgenerated recrystallization to accommodate the strain associated with continued growth of the ordered crystals. Doping with Y is found to maintain an ultrafine ordered microstructure suppressing the occurrence of self-generated recrystallization and, therefore, improving the corrosion resistance.

Effect of acid proticity on the thermodynamic parameters of charge transfer resistance in corrosion and passivation of nickel based glass alloy

“…We note that some interfaces can introduce an order–disorder transition of this two-dimensional layered network into molecules, leading to increased diffusional characteristics and reduced bonding. Moreover, we can observe an order and disorder combined corrosion morphology of dual-phase Ni-based alloy in the passive state 22 , 32 – 37 , 45 – 49 .…”

Correlation Between Microstructural Stability and Properties of Ground State Structures in Ordered Alloys: An Example Derived from the D1a Superlattice of Ni4Mo

“…At the exact stoichiometric composition of Ni 4 Mo, the parent disordered face-centered cubic (fcc) phase is known to transform into the ordered tetragonal D1 a superlattice at a temperature below about 870°C [8]. We have shown in previous studies, that the microstructural instability of the D1 a superlattice during extended aging at high temperatures can preclude the prediction of properties from first-principles calculations [9,10]. In the present study, particular emphasis is placed upon the evolution of the ordered microstructure including: (i) the transition from short-range order to long-range order, (ii) the defect structure, which accompanies the disorder-to-order transformation, and (iii) the mechanism responsible for degrading the tensile properties and corrosion resistance.…”