Effect Of Fe Element On The Corrosion Resistance Of Al-based Amorphous Alloy

Compare to the critical Al-based amorphous alloys, the Al-TM-RE alloys not only have high strength, high hardness, but also have excellent corrosion resistance. A lot of alloys with better glass-forming ability (GFA) and stronger properties have been obtained by adding elements into the Al-TM-RE alloys. The corrosion resistance is a very important property during the using progress. Therefore, in this article, we selected the Al-TM-RE-based alloys as the object, studied the glass-forming ability, microstructure, thermodynamic properties, mechanic properties, electromagnetic properties and electrochemical properties, and so on. At the same time, we have also studied the relationship between the microstructure and properties, the mechanism of corrosion resistance of alloys.The new alloy Al84Ni9Fe1La6 is obtained by using 1 at.% Fe to substitute the Ni in Al84Ni10La6 alloy. The influence of Fe addition on the microstructure is investigated by the X-ray diffraction (XRD) and the dilatometer; the changes of properties caused by the Fe addition are researched by the differential scanning calorimetry (DSC), the scanning electron microscopy (SEM), the electric resistivity test, the magnetism test and the electrochemical corrosion. It is found that the 1 at.% Fe addition will increase the number of medium-range order clusters and reduce the free volume in the Al84N10La6 ribbons. These changes of microstructure improve the glass-forming ability, microhardness, fracture toughness, electric resistivity, absolute diamagnetism and corrosion resistance in 0.1 mol/L NaOH solution of Al84Ni10La6 ribbons.We gained a series of Al88Ni6La6 ribbons from amorphous to crystal through controlling the cooling rate. We studied the effect of cooling rate on the corrosion resistance of Al88Ni6La6 ribbons in 0.1 mol/L NaOH,0.1 mol/L H2SO4 and 3.5 wt% NaCl solutions by the X-ray diffraction (XRD) and electrochemical corrosion; we also investigated the mechanism of corrosion resistance of ribbons using the scanning electron microscopy (SEM), the energy spectrum (EDS), the transmission electron microscopy (TEM). and so on. We found that with the decreasing cooling rate. the corrosion resistances of Al88Ni6La6 ribbons in the 0.1 mol/L NaOH,0.1 mol/L H2SO4 and 3.5 wt% NaCl solutions are weakened. There was no pitting corrosion happened in NaOH and H2SO4 solutions, while pitting corrosion appeared in NaCl solution, indicating that the Al88Ni6La6 ribbons exhibit superior corrosion resistance in the acid and alkali without Cl- ions, while showing slightly lower corrosion resistance in the salt with Cl- ions. During the crystallization process, theα-Al and Al-La phases were precipitated firstly. The Fe atoms enter theα-Al structure which will lead to more uniform passivation film. The Al6Fe phase and nano-phase in the amorphous matrix have the combined action to the corrosion resistance of Al88Ni6La6 ribbons, the property that easy to form oxide film of Al6Fe phase protects the Al88Ni6La6 ribbons from the pitting corrosion. The structure of phases in the matrix formed the crack source in the amorphous matrix. And the difference of corrosion rate between matrix and phases cause the corrosion stress which increases the crack extension. Participates in the amorphous basements can strengthen the ribbons, which cause the enhancement of the microhardness of ribbons.