Effect of Mn Content on the Passivation and Corrosion of Al0.3Cr0.5Fe2MnxMo0.15Ni1.5Ti0.3 Compositionally Complex Face-Centered Cubic Alloys

Abstract

Al0.3Cr0.5Fe2MnxMo0.15Ni1.5Ti0.3 (x = 0, 0.25, 0.5, 1) compositionally complex alloys are synthesized and annealed at 1,070°C to form two-phase alloys with a face-centered cubic (fcc) matrix and a second phases enriched in Al, Ti, and Ni with slightly reduced density, raw element costs, and passivating elements distributed across both phases. The global corrosion resistance is evaluated in 0.01 M and 0.1 M NaCl at both natural pH and pH 4. Overall corrosion resistance is suggested to be optimized at Mn concentrations of 5.0 at%, indicated by pitting potentials comparable to or exceeding those of 316L stainless steel. Improvements in corrosion resistance and optimization of Mn concentration are further assessed by polarization, impedance, and gravimetric analysis after extended aqueous exposure. The fate of individual elements during the dissolution and passivation processes is evaluated with in situ atomic emission spectroelectrochemistry and ex situ x-ray photoelectron spectroscopy. Passivity was derived from combinations of Ti4+, Cr3+, and Al3+ oxides in an undetermined solid solution or complex oxide. Enhanced corrosion resistance is attributed to the improved chemical homogeneity of passivating elements within the two-phase microstructure, while the decreased corrosion resistance of alloys with higher Mn concentrations is attributed to high Mn dissolution rates and/or destabilization of the passive films. The underlying determinants of the role of Mn in the design of corrosion-resistant lightweight compositionally complex alloys are discussed.

Risk analysis of Ex-spool 16” mol: an insight of machine learning and experimental result

“…Also, the presence of manganese and sulfur increases the ability of the metal to adverse the effect of corrosion. The lower amount of manganese (5 %) suggests the exspool tends to rust, although it has a minor contribution to the overall material's degradation [36]. The study [37] shows that Mn remains an essential element in reducing the erosion velocity of sand through the solid strengthening of manganese.…”

A High Throughput Aqueous Passivation Testing Methodology for Compositionally Complex Alloys Using a Scanning Droplet Cell

“…These exact details can be elucidated in follow-on high fidelity studies which can address many of these questions. 42,[44][45][46][47][48][49] Moreover, a similar HTp approach can be developed in sulfate and chloride with a better emphasis on chloride breakdown. Some indicative metrics might differ while others such as self-healing are likely of similar value toward guiding the discovery of improved alloys.…”

“…36 CoCrFeMnNi showed a larger i crit , and lower impedance compared to the thin film CCAs that could be attributed to its 20 at% Mn content, as Mn selectively dissolves with negligible participation towards alloy passivation. 44,45 Suitability of sputtered thin films as surrogates is often a question in corrosion research as far as how accurately they represent a bulk alloy produced conventionally. 54 This is the subject of our separate studies and is beyond the scope of the current manuscript.…”

Elementally Resolved Dissolution Kinetics of a Ni-Fe-Cr-Mn-Co Multi-Principal Element Alloy in Sulfuric Acid Using AESEC-EIS

“…For instance, Mn is desired to stabilize face-centered cubic (FCC) solid solution even though it forms a film detrimental to the protection by passivity. 12,21 Early reports of passivation and oxidation assume the presence of single-element or complex oxides 22 and stoichiometric oxides. 7 In the case of aqueous passivation, surfacesensitive tools must be used because the oxides have a thickness of the order of several nanometers.…”

“…[27][28][29][30] Atomic emission spectroelectrochemistry (AESEC) has demonstrated to be a powerful technique to track the fate of each alloying elements for MPEAs during electrochemical measurements. 21,[31][32][33][34][35] The fate of each element, whether in metal, oxide or solution during spontaneous dissolution, activation and passivation, was ascertained by the AESEC technique. AESEC enables the determination of atoms which are oxidized but not dissolve in solution, i.e., may have reached the surface as an oxidized insoluble species, via AESEC mass-charge balance.…”