Abstract
AA5154 aluminum alloy wall was built using EBAM where the wall’s top layers were alloyed by depositing and then remelting a Mo powder-bed with simultaneous transfer of aluminum alloy from the AA5154 wire. The powder-beds with different concentrations of Mo such as 0.3, 0.6, 0.9 and 1.2 g/layer were used to obtain composite AA5154/Mo samples. All samples were characterized by inhomogeneous structures composed of as-deposited AA5154 matrix with coarse unreacted Mo articles and intermetallic compounds (IMC) such as Al12Mo, Al5Mo, Al8Mo3, Al18Mg3Mo2 which formed in the vicinity of these Mo particles. The IMC content increased with the Mo powder-bed concentrations. The AA5154 matrix grains away from the Mo particles contained Al-Fe grain boundary precipitates. Mo-rich regions in the 0.3, 0.6, 0.9 and 1.2 g/layer Mo samples had maximum microhardness at the level of 2300, 2600, 11,500 and 9000 GPa, respectively. Sliding pin-on-steel disk test showed that wear of A5154/Mo composite reduced as compared to that of as-deposited AA5154 due to composite structure, higher microhardness as a well as tribooxidation of Al/Mo IMCs and generation of mechanically mixed layers containing low shear strength Mo8O23 and Al2(MoO4)3 oxides.
Highlights
The development of new high-strength and temperature-resistant metallic materials is an urgent task faced by specialists working in space, aircraft, and automobile industries.Nowadays, nickel-based, high-temperature strength alloys are widely applied for fabricating gas and steam turbine blades or exhaustive gas heat shields [1]
Coarse light particles and discontinuities can be observed in zone 2 of all samples, which could result from sintering the Mo powder agglomerates and diffusion reaction with Al
The dark contrasting particles can be seen owing to their higher density as compared to the as-deposited A5154 layers and reveal distribution of both unreacted Mo and Al-Mo intermetallic compounds (IMC) formed from the Mo powder-bed
Summary
Nickel-based, high-temperature strength alloys are widely applied for fabricating gas and steam turbine blades or exhaustive gas heat shields [1]. Their working temperatures are less than those of refractory metal aluminides [2,3,4,5]. Due to its low solubility in aluminum, molybdenum forms a number of hard intermetallic Alx Moy compounds (IMCs) that might have been used for reinforcing the aluminum alloy matrix if properly dispersed and distributed in it Such a composite structure can be used for improving both mechanical and functional characteristics of the alloy
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