| Recently, bulk metallic glasses（BMGs） has already generated tremendous interests because of large elastic strain limit, high strength, and high hardness. Usually, plastic deformation of monolithic BMGs are achieved by propagation of highly-localized shear bands although the degree of plastic deformation are large in these shear bands. BMGs exhibit brittle fracture of no macroscopic plastic deformation, during plastic deformation process. And this defect limits the application of BMGs in many engineering fields. Due to the proliferation principle of dislocations in crystal materials by the resistance of the secondary phase. It is an effective method to improve the plasticity of BMGs by the effect of the ductile dendritic crystalline phase with different strengths and elastic moduli, which stabilizes against the shear localization and propagation of critical shear bands and prompts generation and slippage of multiple shear bands. A new kind of materials named as in-situ metallic glass matrix composites（MGMCs） with dispersed secondary phases have been developed. Which enhances the room-temperature ductility in a large extent. But the corrosion behavior of in-situ MGMCs has not been investigated to a reasonable extent. Only a few studies have been reported for in-situ MGMCs so far, and most of work has been focused on monolithic BMGs. In this study, the corrosion behavior of Ti40Zr24V12Cu5Be19 and Ti46Zr20V12Cu5Be17 in-situ MGMCs in different solutions were studied as well as the effect of the solution content on the corrosion behavior of in-situ MGMCs and how the corrosion behavior of these composites evolves with the sample sizes in the same solution.The ingots of Ti40Zr24V12Cu5Be19 and Ti46Zr20V12Cu5Be17 in-situ MGMCs were fabricated using arc-melt casting. The electrochemical tests and chemical tests were carried out in different solutions at room temperature. The methods of electrochemical tests included potentiodynamic polarization tests（Tafel slope method）, the electrochemical impedance spectroscopy（EIS） tests, and potentiostatic polarization curves. The immersion tests in different solutions open to air at room temperature for 7 days were conducted on these samples. The volume content of H2SO4 and HCl solutions were 0.1 %, 1 %, and 10 %. And the content of Na OH and NaCl solutions are 40 % and 3.5 %, respectively. The sample were casted into F 2, F 3, and F 6 mm rods, respectively. Further analysis about the structure, surface morphology, and element distribution were obtained by using X-ray Diffractometry（XRD）, with monochromated Cu-Ka radiation（l=0.1542 nm）, scan-electron microscope（SEM） coupled with energy-dispersive X-ray（EDS） and X-ray photoelectron spectroscopy（XPS） with Al-Kα（h? = 1486.6 e V） radiation. The experimental results are as follows:1. In the tests of Ti40Zr24V12Cu5Be19 in-situ MGMCs in 10 % H2SO4 solution, 40 % NaOH, and 3.5 % NaCl. The best corrosion resistance appears in the 3.5 % NaCl solution. The corrosion-current-density（icorr） values and passivation-current-density（ipass） values in the 3.5% NaCl are of the order of 10-7 A/cm2 and 10-6 A/cm2. But their resistance to chloride-induced pitting is very poor in the NaCl solution. In the Na OH solution, the corrosion resistance and passivation properties are poorest and both value are of the order of 10-4 A/cm2. And in amorphous matrix, the corrosion products had a better corrosion resistance properties compared with crystalline dendrites. XRD results indicated that passivation products with excellent corrosion resistance properties were generated, which aroused a galvanic effect and it further accelerate the rate of secondary phase.2. For Ti46Zr20V12Cu5Be17 in-situ MGMCs, with a elevation of the acid content, the corrosion resistance properties had a significant decrease in either H2SO4 solution or HCl solutions. In the same concentration, it had a the corrosion resistance and passivation properties in the H2SO4 solution. EDS results showed the amount of Ti and Zr element have a obvious decrease with a elevation of the acid content, which leads to a declining of compactness of passive film and it add to a fast rate for corrosion process.3. For Ti46Zr20V12Cu5Be17 in the same acid content, the F 6 mm sample had a excellent corrosion resistance and passivation properties. icorr and ipass values are of the order of 10-6 and 10-5 A/cm2. The corrosion resistance and passivation properties of F 2 mm sample are poor, and icorr values and ipass values are of the order of 10-5 A/cm2 and 10-3 A/cm2. By the results of XPS analysis, it is found a obvious different between passivation products in sample surface. F 6 mm sample had a well compactness passive film, which provide a better protective effect for surface. |
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