Effects of Varying Copper Content on the Microstructure and Mechanical Properties of FeCoNiCu_(x)

Five sets of high entropy alloys(HEAs)FeCoNiCu_(x)(x=0.5,1.0,1.5,2.0,2.5)were produced by vacuum induction smelting.The effects of Cu content on the microstructure and mechanical properties of the alloys were interrogated by X-ray diffractometer(XRD),field scanning electron microscope(FESEM)and tensile mechanical test.The result shows that the HEAs form single FCC solid solution phase.With the increase of Cu content,the diffraction peak first deviated to the right and then shifted to the left.The alloys changed from equiaxed crystal structure to refined dendritic crystal structure,as Cu content increased.A large number of Cu atoms are isolated in the inter-crystalline region.The tensile mechanical tests show that with the increase of Cu content,the ultimate tensile strength first increased and then decreased.When x is 2.0,the ultimate tensile strength reaches a maximum of 473 MPa,the percent elongation is 43.0%,and the fracture presents ductile behaviour.

Multifunctional interstitial-carbon-doped FeCoNiCu high entropy alloys with excellent electromagnetic-wave absorption performance

Electromagnetic-wave absorbing(EMA)materials that have efficient absorption performances,great me-chanical properties and chemical stability are rare and yet essential for communication security and pro-tection.Herein,flaky interstitial-carbon-doped FeCoNiCu high entropy alloys(HEAs)as novel EMA ma-terials were successfully prepared by high-energy ball-milling method.Interstitial-carbon doping as a modulating approach impacted the phase forming,morphology and electromagnetic properties of Fe-CoNiCu HEAs.Impedance matching was significantly optimized via tuning interstitial carbon contents.The carbon-doped FeCoNiCu HEAs with appropriate carbon contents delivered superior EMA performance compared with other HEAs EMA materials.Strong reflection loss as low as-61.1 dB in the Ku band,broad effective absorption bandwidth of 5.1 GHz was achieved for FeCoNiCuC_(0.04).Moreover,the carbon-doped FeCoNiCu HEAs exhibited excellent mechanical hardness and chemical stability.This work not only suggests that interstitial-carbon doping is an available approach to tuning electromagnetic properties of HEAs,but also presents carbon-doped FeCoNiCu HEAs as promising EMA materials for civilian and mili-tary due to the efficient absorption,broad bandwidth,great durability and stability.