The Corrosion Behaviors Of In-situ Zr-Based Metallic Glass Matrix Composites In Different Solutions

The emergence of the bulk metallic glasses(BMGs) broken the situation of crystal metal material in the engineering construction. It have attracted the attention of a large number of researchers on the preparation and properties of BMGs. So far, there have been invented quite a number of techniques to prepare BMGs, a great breakthrough has been made in the size, it has been reported that the maximum size has reached to 80 mm. The BMGs exhibit many excellent properties that crystal alloys can't reached, such as high strength, high hardness, high corrosion resistance and excellent magnetic properties, due to the special structure of BMGs while traditional crystal materials do not have, that is to say, the structure of BMGs is a single phase, which result in the internal structure of BMGs have no defects like crystal materials, such as dislocation, grain boundary. The good performance make BMGs became the most potential engineering material in recent years. Although there are many advantages in the properties for the BMGs, the applications of the BMGs in many fields are limited due to the brittle fracture at room temperature. In order to overcome the shortcoming, improve the ductility of BMGs at room temperature. The metallic glass matrix composites(MGMCs) are prepared by introducing the second phase in the amorphous matrix, combining the strength and plasticity to enlarge the application range of the BMGs.The Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 MGMCs with high strength and excellent plasticity are prepared by copper suction casting, using the analysis methods, such as X-ray diffraction(XRD), Scanning electron microscope(SEM), to affirm the structure phase of the Zr-based MGMCs. The analysis and discussion about the corrosion behavior of the Zr-based MGMCs in different corrosive environment can by the electrochemical testing methods, like potentiodynamic polarization curves and impedance spectroscopy, in addition, the chemical immersion tests to be used further demonstrate the corrosion results. After corrosion occurred, the surface corroded morphology on the metallic glass matrix composites can be seen by the SEM detection, combining the above analysis means to summarize the corrosion occurred mechanism for the MGMCs.The corrosion resistance in different concentration contain NaCl solutions for Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 MGMCs have been investigated, the results showed that the corrosion resistance of Zr-based MGMCs in different content NaCl solution is not correspond with the NaCl increased, while appears a parabolic trend. In short, when the NaCl content in aqueous solution is 5%, the corrosion resistance of MGMCs is the worst, while the corrosion resistance in the lowest concentration of 1% and the highest concentration of 15% are both good. Based on the analysis for the dielectric in aqueous solution, the corrosion resistance of the Zr-based MGMCs in NaCl solution are not only related to the solubility of oxygen, but also related to the concentration of chloride ion in aqueous solutions.Comparing the corrosion resistance behaviors of Zr-based MGMCs in different pH value environments. It was found that the results for the corrosion resistance of the amorphous sample in NaOH solution through potentiodynamic polarization curve and surface corroded damage degree obtained by SEM are not agreement. Moreover, it can be found that the chloride ions not only on the crystal materials surface, but also on the metallic glasses and related composites surface, have very strong corrosion damage ability. According to the surface corroded morphology in the chloride-containing solutions, it was found that the amorphous matrix would be preferentially dissolved compared to the dendrites, the corrosion resistance difference between the amorphous matrix and dendrites are mainly related to the distribution of metal element, like Zr and Be, on the amorphous matrix and dendrites.