Effect Of Mo And Nb Addition On Glass Forming Ability,thermal Ability And Corrosion Resistance Of ZrCu-based Amphorous Alloy

ZrCu-based bulk metallic glass(BMG) is widely developed in recent years, and micro-alloying method is an important method on BMG research. In this thesis, ZrCu-based BMG was studied by micro-alloying method. The influence of Mo, Nb on glass-forming ability(GFA), thermal stability and corrosion resistance of Zr47Cu44Al9 matrix alloy were discussed.BMG samples were prepared by copper mold suction casting method, and analyzed by X-ray diffraction(XRD), differential scanning calorimeter(DSC), electrochemical detection equipment and so on. The results were shown as follows.Mo addition significantly affects the GFA of the alloy. The alloy with 2% Mo presents the best GFA, and critical dimension of amorphous samples is increased from 4 mm of that to 6mm for Zr47Cu44Al9. The characteristic of the alloy are sensitive to the composition of Mo. For the alloy with 3% Mo, none of amorphous phase is detected in the 4mm sample.Characteristic temperature, the apparent activation energy(Eg, Ex, Ep), and the local activation energy E? in the crystallization process were calculated by Losacka, Kissinger and Doyle equation. The results indicate that the thermal stability of alloy is improved with 2% Mo.Corrosion experiments results show that the alloys with different Mo content have worse corrosion resistance in containing chloride ion media, including HCl and NaCl etching solutions, but better corrosion resistance in HNO3, NaOH and H2SO4 solutions. We conclude that there is a strong correlation between corrosion resistance of such alloy with the solution system. However, the effect of addition amount of Mo is not obvious. Furthermore, compared with the other alloys with same composition, the integrated corrosion resistance of(Zr47Cu44Al9)98Mo2 BMG is better than other alloy in this system.The GFA of the alloy is significantly improved with appropriate adding amount of Nb elements. The GFA firstly increases and then decreases with the increase of Nb addition from 1% to 5%. For the range of addition amount from 1% to 4%, the amorphous alloys are critical dimensions up to 5mm or more. For the alloy with 2% Nb, the pure amorphous critical diameter can reach more than 8 mm. The influence of Nb element on GFA of amorphous alloy is superior to Mo element.The thermal stability results display that Nb addition significantly improved the thermal stability of the alloy. The Eg, Ex, Ep of(Zr47Cu44Al9)98Nb2 alloy calculated by Kissinger method is 302.7 KJ / mol, 445.85KJ/mol and 389.21KJ/mol, respectively.The corrosion resistance of the alloy with Nb addition shows as similar as the alloy with Mo addition. It means that the alloys have worse corrosion resistance in HCl and NaCl etching solutions, but better corrosion resistance in HNO3, NaOH and H2SO4 solutions. However, two types of alloys are also significantly different. It means that the corrosion resistance of this system is related to not only solution system but also the addition amount of Nb and the state of samples.