Abstract
Nickel Aluminum Bronze (NAB) and Manganese Aluminum Bronze (MAB) are high-alloyed bronzes that are increasingly employed in several industrial sectors, mainly related to hostile environments due to their excellent properties against corrosion, cavitation, erosion and improved mechanical properties in relation to other copper-based alloys. These materials are very sensitive against thermal treatments due to a multiphase microstructure in as-cast condition. To contribute to the knowledge of the behavior of both alloys, the effect of thermal treatments on the corrosion behavior of NAB (CuAl10Fe5Ni5) and MAB (CuMn12Al8Fe4Ni2) was studied. As-cast material was subjected to various combinations of quenching and quenching and tempering at 850 °C and 600 °C. Corrosion testing was carried out using simulated sea and fresh water. The microstructures of the as-cast and heat-treated samples were characterized by metallography using two chemical agents with FeCl3 and NH4OH solutions and examination by optical and scanning electron microscopy. The major effect of thermal treatments on corrosion was found in influencing the amount and distribution of β-phase, which is prone to selective corrosion in both electrolytes.
Highlights
Nickel Aluminum Bronzes (NAB) and Manganese Aluminum Bronzes (MAB) are copper-based alloys with a relevant content of Ni, Al, Mn and Fe
The major effect of thermal treatments on corrosion was found in influencing the amount and distribution of β-phase, which is prone to selective corrosion in both electrolytes
Both etchants were applied to the micrographs, micrographs, which which are are presented presentedin in
Summary
Nickel Aluminum Bronzes (NAB) and Manganese Aluminum Bronzes (MAB) are copper-based alloys with a relevant content of Ni, Al, Mn and Fe. Besides the cooling inherent to the solidification process itself during casting, further thermal influences may occur during manufacturing or in service and welding is one of the most relevant, with important consequences for the corrosion behaviour of these alloys [14,15,16,17] The aim of this investigation is the direct comparison of corrosion behaviour of NAB and MAB, with identical thermal history in well-defined yet practically relevant media (simulated fresh water, simulated sea water), under identical and constant oxidative conditions (potentiostatically), for extended time (days). The microstructure of MAB is similar to that of NAB, influenced by the composition anddissolved It isthe dominated α-phase, which is copper-enriched, are During further cooling, β-phase by decomposes into α-phase and κ-phases, andcoexisting by β-phase.asWhen the melt cools down rapidly, martensitic is preserved.
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