Effect of Co addition on the microstructure, thermal stability and anti-corrosion properties of AlNiZrYCox high-entropy metallic glass ribbons

Abstract

In this current research, the effect of Co addition on the microstructure and anti-corrosion properties of equiatomic AlNiZrY high-entropy metallic glass (abbreviated to HE-MG) ribbons were investigated. Also, the thermal stability and crystallization activation energy of these HE-MG ribbons have been studied. Ribbons of composition (Al1/4Ni1/4Zr1/4Y1/4)100-xCox (x= 0, 5, 8, 12) were synthesized via arc-melting method and melt-spinning technique. By increasing the content of Co, we found that the melt-spun equiatomic AlNiZrY and Co-containing AlNiZrY HE-MG ribbons could still remain amorphous state. The thermal stability of ribbons were conducted by means of a differential scanning calorimeter (DSC), which suggested that the thermal stability of four kinds of HE-MG ribbons is higher than common Al-Ni-based amorphous alloys. The maximum apparent activation energy of crystallization through thermodynamic analysis at different heating rates can reach ∼630 kJ/mol for (Al1/4Ni1/4Zr1/4Y1/4)92Co8 HE-MG ribbons. The microstructure characterization of each HE-MG ribbon before and after one-day corrosion immersion was done by scanning electron microscopy (SEM). In order to evaluate the microhardness and corrosion resistance of the as-received HE-MG ribbons with and without the addition of Co, the microhardness measurements and the electrochemical corrosion tests in 3.5 wt.% NaCl solution were carried out. The results revealed that the average microhardness value of HE-MG ribbons are all above 470 HV0.1, regardless of whether the ribbons immersed in corrosive media for one-day immersion or not. The corrosion current density of (Al1/4Ni1/4Zr1/4Y1/4)88Co12 HE-MG ribbons is around 0.46 μA/cm2, which possesses the sterling anti-corrosion property and opens vital possibilities for the development of high-performance metal coatings under the condition of harsh marine environment.