中國有色金屬學報(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 20 No. 2 February 2010 |
N. SAITO2, YUAN Yu-chun(袁玉春)1, Y. NISHIDA2
（1. College of Materials Science and Engineering, Hohai University, Nanjing 210098, China;
2. National Institute of Advanced Industrial Science and Technology, 2266-98, Anagahora, Shimoshidami, Moriyama-ku, Nagoya 463-8560, Japan）
Abstract:Ultrafine-grained(UFG) hypereutectic Al-23%Si (mass fraction) alloy was achieved through equal-channel angular pressing(EACP) procedure. And the electrochemical properties after various ECAP passes were investigated in neutral NaCl solution. Potentiostatic polarization curves show that the corrosion potential of the ECAPed sample after 4 passes decreases markedly, while the corrosion current density reaches 1.37 times that of the as-cast alloy. However, the φcorr and Jcorr values after 16 passes are improved and approach those of the as-cast alloy. Immersion tests also show that the mass-loss ratio of ECAPed alloy decreases with increasing the pressing pass, which is lowered to 28.7% with the increase of pass number from 4 to 16. Pitting susceptibility of the ECAPed alloy after initial 4 passes is boosted, due to the presence of biggish voids resulted from the breakage of brittle large primary silicon crystals during ECAP. Increasing ECAP pass makes the voids evanesce and results in the homogeneous ultrafine-grained structure, contributing to a higher pitting resistance. These results indicate that enough ECAP passes are beneficial to increasing corrosion resistance of the hypereutectic Al-23%Si alloy.
Key words: aluminum casting alloys; ECAP; corrosion behavior; ultrafine grained microstructure
