Effects of Yttrium on the Microstructure and Corrosion Behavior of Pb-39Mg-10Al-1B-Y Alloys

摘要

Pb-39Mg-10Al-1B-Y alloys with Y = 0, 0.2, 0.4, 0.6, 0.8, and 1.0 (wt.%) were fabricated by melting and casting. The microstructure and electrochemical corrosion behavior of the Pb-39Mg-10Al-1B-Y alloys in a 3.5 wt.% NaCl solution were investigated using x-ray diffraction, electron probe microanalysis, and scanning electron microscopy, polarization curve tests, electrochemical impedance spectroscopy (EIS), and electrochemical noise (EN). Mg2Pb + Pb eutectic gains are refined, and the distribution of Mg17Al12 + Mg eutectic gains becomes continuous by with the addition of Y. The polarization curves, EIS results and EN results show that the corrosion resistance of the alloys with various Y concentrations is in the order 0.8 > 1 > 0.6 > 0.4 > 0.2 > 0. The primary corrosion behaviors of Pb-39Mg-10Al-1B-Y alloys when Y <= 0.4 wt.% and Y > 0.4 wt.% are general corrosion and localized corrosion, respectively. There is a Mg-Mg2Pb galvanic cell present with Mg2Pb as the cathode and Mg as the anode. Moreover, Cl- can accelerate the corrosion of the Mg phase.