Microstructure, magnetic properties, corrosion resistance and catalytic activity of dual-phase AlCoNiFeTi and AlCoNiFeTiSi high entropy alloys

Abstract

The high entropy AlCoFeNiTi and AlCoFeNiTiSi alloys were prepared by two methods to determine the influence of the cooling rate on the structure and properties. The Mössbauer spectra of AlCoFeNiTi alloys showed the coexistence of a nonmagnetic part with a magnetic hyperfine portion. The spectra for AlCoFeNiTiSi alloy in an as-cast and plate states contain only nonmagnetic components. The X-ray diffraction analysis confirmed that the silicon addition drastically changes the phase composition of AlCoFeNiTi alloy. Whereas alloy without Si was characterised by the coexistence of L21 and BCC phases, the addition of silicon resulted in the formation of Ti-rich HCP and Al-rich B2 phases. AlCoFeNiTi plate exhibits a high saturation magnetisation value of 29.83 emu/g and the best corrosion resistance (polarisation resistance of about 38.6 kΩcm2 and corrosion current density of 0.77 μA/cm2). The highest hardness (1096 HV) was achieved for AlCoFeNiTiSi plate, which is related to the phase composition changes generated by Si addition. The influence of the Si addition on the properties of studied alloys was also confirmed in the decolourisation of Rhodamine B using a modified photo-Fenton process. The decolourisation efficiency within 60 min was 92% for AlCoFeNiTiSi alloy, and 95.5% for the AlCoFeNiTi alloy.