Intergranular corrosion of a curved ∑=5 grain boundary in an FeSi alloy bicrystal

Abstract

Intergranular corrosion plays an important role in the cohesion and thus, in the use of polycrystalline metals and alloys. Due to the differences in structure and energy, the environmental attack of grain boundaries can differ in individual cases. The orientation dependence of intergranular corrosion has already been studied: however, attention was mainly paid to symmetrical grain boundaries. Minima of the penetration depth or the width of the etched boundary groove corresponding to the minima of the measured boundary energy were found at certain tilt grain boundaries in aluminum, Cr-Ni-austenitic stainless steel, niobium, and copper and [alpha]-Cu-Al alloy. Low values of the etch groove depth were also found at the low-[Sigma] grain boundaries in a polycrystalline Fe-Ni-Cr alloy. It was surprising to find that the maxima of penetration depth were reported for the low energy (013), (012) and (023) symmetrical tilt grain boundaries in an austenitic stainless steel containing silicon. With an exception of Ogura's work the sets of bicrystals containing a single symmetrical grain boundary were etched and the results were then compared. In the present work the corrosion behavior of the 36.9[degree] symmetrical and asymmetrical tilt grain boundaries in one sample were studied on a single curved grain boundary.