The corrosion behavior of Fe-based shape memory alloys

Fe-30Mn-6Si, Fe-30Mn-6Si-5Cr and Fe-13Mn-5Si-12Cr-5Ni shape memory alloys were prepared by a VIM technique. The various corrosion tests were conducted to investigate the corrosion behaviors of these alloys. Experimental results show that in 3.5% NaG solution, the Fe-13Mn-5Si-12Cr-5Ni alloy had the best chemical corrosion resistance, whereas the Fe30-Mn-6Si-5Cr alloy was locally attacked, forming many corrosion pits after immersion test. In addition, the detachment of the corrosion product covering the Fe-30Mn-6Si alloy caused an abrupt increase in the weight loss. After 2 h of heat treatment at 1000 degreesC, the corrosion potential of the Fe-30Mn-6Si alloy increased due to the formation of alpha-ferrite, while the Fe30-Mn-6Si-5Cr alloy became more active. In the stress-corrosion cracking test, the Fe-13-Mn5-Si-12Cr-5Ni alloy, having the highest fracture stress in the atmosphere among these alloys, exhibited the largest decrease in fracture stress in the saturated H'S solution due to the existence of alpha-martensite. (C) 2002 Elsevier Science Ltd. All rights reserved.