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Al-Al4C3 metal matrix composites reinforced by Al4C3 nanoparticles

wallpapers News 2021-05-08
Al-Al4C3 metal matrix composites reinforced by Al4C3 nanoparticles were prepared by the powder metallurgy method. The well-dispersed coherent Al4C3 phase was formed during the preparation process, which ensured good interface bonding and obtained good mechanical properties. 1 Yield strength (YS) of wt strengthening material. The % of C reaches 275 MPa, the tensile strength (UTS) is 295 MPa, and the elongation (A) is 14%, which means that the material can compete with an equal number of carbon nanotubes (CNTs/Al) reinforced aluminum matrix.
To analyze the thermal stability, the Al-Al4C3 composites were exposed to temperatures of 250°C, 500°C and 620°C for 5 hours, followed by gradual cooling to room temperature in a furnace. The composite has high structural stability (the subgrain size is about 0.82 μm after heat treatment at 250℃ and does not change at 500℃), and its mechanical properties remain unchanged at 500℃. After thermal exposure at 620℃, the subgrain size increases nearly twice (about 1.93 μm) and the substructure also degrades, but the material maintains good YS(about 220 MPa) and UTS(about 245 MPa) values. Even after heat treatment, the microstructure and mechanical properties of composites are obviously determined by the in-situ formation of the Al4C3 phase. Therefore, we believe that Al-Al4C3 composites may be a good substitute for CNTs/Al composites, depending on the purpose of their application.
In a multimode cavity reactor, the phase of pure binary aluminum carbide Al4C3 can be synthesized in a vacuum by microwave heating for 30 minutes. The success of the reaction depends on the use of finely separated starting materials of aluminum and graphite, both of which combine effectively with the microwave field. The yellow-brown powder was characterized by powder X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray spectroscopy, thermogravimetric differential thermal analysis and Raman spectroscopy. The powder is composed of hexagonal single crystals with a diameter of tens of microns (rhombohedral space group R and bonded long crystals] M; Z = 3; A = 3.33813(5) A, C = 25.0021(4) A), stabilized to 1000℃ in air, argon and nitrogen. The equivalent microwave reactions of these elements in the air lead to the formation of oxidized carbide phases Al2Oc and Al4O4C.