Effect of interlamellar spacing on the mechanical properties of 0.65% C steel

The mechanical properties of a steel containing a nearly fully pearlitic structure have been examined as a function of the interlamellar spacing. The steel had been heat-treated at different austenitization temperatures in order to obtain varying interlamellar spacings. It was observed that hardness and yield strength follow a HallPetch type of relationship with respect to the interlamellar spacing but the ultimate tensile strength (UTS), percent elongation and impact toughness did not do so. It was noted that, below a critical size of interlamellar spacing, the UTS, impact toughness and ductility remained invariant to the interlamellar spacing. The results have been explained on the basis of a microstructure-thermal residual stress relationship. (C) 2001 Elsevier Science Inc. All rights reserved.