Microstructure dependence of electrochemical corrosion resistance for rapidly solidified Ti50Al48Mo2 alloy

The rapid solidification of undercooled liquid Ti50Al48Mo2 alloy was achieved by the electromagnetic lev-itation (EML) technique. At small and medium undercoolings, primary (beta Ti) dendrite reacted with sur-rounding liquid to drive a peritectic transformation into the (alpha Ti) phase. The solutal Mo and Al segrega-tions were located within the dendrite center and the grain boundary during peritectic transformation, consequently B2 phase in the dendrite center and gamma phase at the grain boundary formed. Once under -cooling exceeded 253 K, the peritectic transformation was completely inhibited, and the formation of the B2 phase and gamma phase was completely suppressed. The ultrafine eutectoid structure was formed and a complete solute trapping effect was realized. Homogeneous solute distribution facilitated the forma-tion of thicker passivation film with lower defect density and higher film resistance on the alloy surface. Moreover, this weakened micro-galvanic effect reduced the susceptibility to pitting corrosion, and conse-quently the corrosion resistance of the alloy was improved.(c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.