Influence of Density and Sintering Temperature on Monotonic, Cyclic, and Low Cycle Fatigue Behaviour of FL4405 High Strength PM Steel

Abstract

Density and sintering temperature effects were investigated with FL4405 low alloy PM high strength steel. Composition, microstructure, image analysis, monotonic and cyclic stress-strain behaviour, low cycle fatigue, and macro- and microfractography were evaluated. Density levels of 7·0 and 7·4 g cm⁻³ and sintering temperatures of 1120 and 1315°C were investigated. The increased density resulted in smaller pore size and pore volume while the increased sintering temperature resulted in greater pore roundness. All final fracture surfaces were brittle at the macroscale while exhibiting ductile dimpling at the microscale. Low cycle fatigue surfaces contained principally ductile dimples with no striations or benchmarks. Increasing the density resulted in significantly higher tensile strength, elastic modulus, ductility, and low cycle fatigue resistance. Increasing the sintering temperature, and hence increasing pore roundness, resulted in additional enhancement of these properties. However, this increase was not as significant as the density increase. PM/0769