2010 Volume 50 Issue 4 Pages 607-612
The structure–property relations of V-added AISI 4335 steel forgings tempered at different temperatures have been examined to delineate the effect of tempering on their ductility and toughness characteristics. The experimental work involved characterization of the microstructures and determination of hardness, tensile properties, impact toughness and plane strain fracture toughness of a series of hardened and tempered samples. The tempering treatments were carried out at eight different temperatures in the range of 633–833 K. The obtained results have shown that hardness and strength decrease in a monotonic fashion with tempering temperature while impact toughness and ductility increase with increasing tempering temperature with an inflection around 753 K. Analyses of the results highlight that the variations of impact toughness and ductility with tempering temperature possess the potential to directly reveal the embrittlement temperature range. It has been also found here that the embrittlement temperature range can be delineated from the variation in the rate of change of fracture toughness with tempering temperature. These observations have been discussed considering the energy absorbed by the initiation and growth of cracks during fracture of a specimen by tensile, impact and fracture toughness tests.