Effect of different annealing atmospheres on crystallization and corrosion resistance of Al 86Ni 9La 5 amorphous alloy

Abstract

The effect of different annealing atmospheres (H 2, air, Ar and N 2) on precipitated phases, corrosion resistance and hardness of Al 86Ni 9La 5 amorphous alloy was investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetry (TG), electrochemistry experiment and microhardness tester. During annealing at 523 K, the primary crystallized fcc-Al is independent on the annealing atmospheres. During annealing at 584 K, the final crystalline phases, i.e. fcc-Al + Al 11La 3 + Al 3Ni, are also independent on the different annealing atmospheres. However, during annealing at 523 K, H 2 and air can promote the eutectic crystallization process, and induce the formation of metastable Al 3Ni 2 phase. The promoting effect of different annealing atmospheres is in the order of H 2 > air > Ar > N 2. The microhardness and corrosion resistance in the 3.5 wt.% NaCl solution are improved by annealing in H 2 and air atmospheres. The property promotion caused by annealing process can be ascribed to the formation of nanocrystalline phases, which is possibly helpful to develop the alloy's application in the seawater environment.