Effect of Copper Addition on the AlCoCrFeNi High Entropy Alloys Properties via the Electroless Plating and Powder Metallurgy Technique

Abstract

To improve the AlCoCrFeNi high entropy alloys’ (HEAs’) toughness, it was coated with different amounts of Cu then fabricated by the powder metallurgy technique. Mechanical alloying of equiatomic AlCoCrFeNi HEAs for 25 h preceded the coating process. The established powder samples were sintered at different temperatures in a vacuum furnace. The HEAs samples sintered at 950˚C exhibit the highest relative density. The AlCoCrFeNi HEAs model sample was not successfully produced by the applied method due to the low melting point of aluminum. The Al element’s problem disappeared due to encapsulating it with a copper layer during the coating process. Because the atomic radius of the copper metal (0.1278 nm) is less than the atomic radius of the aluminum metal (0.1431 nm) and nearly equal to the rest of the other elements (Co, Cr, Fe, and Ni), the crystal size powder and fabricated samples decreased by increasing the content of the Cu wt%. On the other hand, the lattice strain increased. The microstructure revealed that the complete diffusion between the different elements to form high entropy alloy material was not achieved. A dramatic decrease in the produced samples’ hardness was observed where it decreased from 403 HV at 5 wt% Cu to 191 HV at 20 wt% Cu. On the contrary, the compressive strength increased from 400.034 MPa at 5 wt% Cu to 599.527 MPa at 15 wt% Cu with a 49.86% increment. This increment in the compressive strength may be due to precipitating the copper metal on the particles’ surface in the nano-size, reducing the dislocations’ motion, increasing the stiffness of produced materials. The formability and toughness of the fabricated materials improved by increasing the copper’s content. The thermal expansion has increased gradually by increasing the Cu wt%.

Microstructural evolution in CoCrFeNi and CoCrCuFeNi alloys processed by autogenous fusion welding

“…The higher hardness and strength are observed in CoCrFeNiCu BM could be due to the smaller grain size that induces Hall-Petch strengthening. Moreover, the addition of Cu will increase the lattice strain that would further improve the strengthening [30]. Only a marginal reduction in UTS (512 MPa), YS (270 MPa) and % E ( ≈ 50%) are observed in welded CoCrFeNi alloy as compared to its BM.…”

Homogeneous dispersion and mechanical performance of aluminum reinforced with high graphene content

“…This may be attributed to the grain refinement of the particles due to the rolling process, which enhances the hardness according to the Hall Petch equation. [24][25][26][27] The hardness of the aluminum increased after rolling from 82 to 118 with 43.9%. For the sample reinforced with 10% copper, the hardness increased from 93 to 133 HV, with 43%.…”

Impact of Graphene and Hot-Rolling on the Microstructure and Mechanical Properties of Aluminum Matrix Nano-Composite

“…The results show a clear improvement in the hardness values for all samples, starting from pure aluminum up to1.5% graphene sample. This may be attributed to the grain re nement of the particles due to the rolling process, which enhances the hardness according to the Hall Petch equation [11][12].…”