Local plastic deformation in the vicinity of grain boundaries in Fe–3 mass% Si alloy bicrystals and tricrystal

Nanoindentation was used to study incipient plastic deformation in the vicinity of grain boundaries of different character in Fe–3 mass% Si alloy bicrystals and tricrystal. Pop-in events associated with the grain boundaries were observed in the load–displacement curves. From the pop-in hardness values, the critical stresses required to propagate the yield past the grain boundary were estimated to be in the range of approximately µ/400–µ/130 (where µ is the shear modulus) depending on the grain boundary character: the special boundaries usually had higher critical stresses than the general boundaries. A Hall–Petch (H–P) type relationship was found between the hardness and the distance of the indenter to the grain boundary. The H–P slopes obtained were approximately one order of magnitude lower than the macroscopic value of the H–P slope for the Fe–3 mass% Si alloy, and were generally lower for general grain boundaries than for special boundaries.