Two amorphous ribbons with the compositions of Al88Ni6La6 and Al86Ni6La6Cu2 were made using the melt-spun method,and their thermal response and electrochemical behavior were studied comparatively.Differential scanning calorimetry(DSC)and electrochemical polarization measurements indicated that Al86Ni6La6Cu2 exhibited slightly higher crystallization temperature(Tx),lower melting point(Tl)and better corrosion resistance in 0.01 mol·L-1 NaCl alkaline solution.These results demonstrated that Cu(2%)addition could slightly promote the glass forming ability,but it could greatly improve the corrosion resistance of Al88Ni6La6 alloy in 0.01 mol·L-1 NaCl alkaline solution.
The effects of crystallization on the corrosion resistance of a Cu52.5Ti30Zr11.5Ni6 bulk amorphous alloy in 1 mol/L HCl, and 6 mol/L NaOH solutions were studied. The amorphous alloy was identified by differential thermal analysis(DSC) and by X-ray diffraction(XRD). The partially and fully crystallized alloys were prepared by controlling the annealing temperatures at 738 and 873 K for 1 and 12 min, respectively, and the corrosion resistances of those annealed alloys were compared with that of the amorphous alloy by immersion test and potentiodynamic measurements in 1 mol/L HCl and 6 mol/L NaOH solutions. The results show that the partially crystallized alloy exhibits high corrosion resistance, whereas full crystallization results in deteriorated corrosion resistance compared with that of the as-cast amorphous alloy.
The diffusion bonding of γ-TiAl alloy to Ti-6Al-4V alloy at different temperatures ranging from 1 073 to 1 173 K under an applied stress of 100 MPa for 2 h was studied. The observation of the microstructure reveals that sound joints between the γ-TiAl alloy and the Ti-alloy without any pores or cracks can be achieved through diffusion bonding at temperatures over 1 073 K under the applied stress of 100 MPa for 2 h. The bond is composed of two zones, and its width increases with the increase of bonding temperature. The EDS chemical composition profiles indicate that there is a diffusion flux of Al atoms from γ-TiAl alloy towards the Ti alloy and of Ti atoms in the opposite direction. The three point-bending of the joints bonded under different conditions was tested and the fracture mode was analyzed by SEM observation.
