Tempering effects on the tensile response and fatigue life behavior of a sinter-hardened steel

The mechanical behavior of a sinter-hardened steel has been evaluated for d ifferent tempering conditions. Microstructural changes, as a consequence of the post-sinter-hardening treatments, were found to significantly affect t he hardness, tensile stress-strain response and high-cycle fatigue resistan ce of the material. Optimum tempering parameters were found to depend stron gly on the service conditions: monotonic or cyclic loading. The material be havior is discussed and rationalized considering: (1) sintering necks as th e load bearing units of the sintered material, (2) the role of pore tips as micronotches on these connecting regions, and (3) notch effects (strength, ductility and fatigue sensitivity) at the local level of sintering necks a s critical for controlling the macroscopic mechanical properties. (C) 2000 Elsevier Science S.A. All rights reserved.