Corrosion Behavior of Heat‐Treated Fe‐Based Shape Memory Alloys

Abstract

The influence of various heat treatments on the corrosion behavior of a novel iron‐based shape memory alloy (Fe‐SMA), Fe‐17Mn‐6Si‐10Cr‐4Ni‐1(V,C), used as prestressing elements in civil engineering was examined through electrochemical corrosion methods. SMAs were subjected to two different electrolytes: saturated Ca(OH)2 solutions with and without chlorides to mimic the conditions in concrete. Two specific heat treatments were applied to the Fe‐SMA, which resulted in a change in grain size and precipitation of secondary phases. Furthermore, conventional structural steel, B500B, was utilized as a reference material. The results reveal that the heat treatments did not significantly change the corrosion rates of these alloys in Ca(OH)2 solution compared to B500B when chlorides were absent. However, the presence of chloride ions suppressed the passivity of B500B and promoted the localized corrosion (pitting and intergranular) of the Fe‐SMAs, among which the solutionized alloy showed significantly higher resistance to the pitting. It was demonstrated that the heat treatments and, consequently, microstructural characteristics influence the pitting behavior of these alloys.