Abstract
Phosphorus alloyed sintered steels of chemical composition in the range 0·25–0·7 wt-%C and 0·45–0·8 wt-%P produce alloys with pore morphologies characterised by shape factors varying between 0·52 and 0·68 and microstructures characterised by different percentages of phases with high (pearlite and phosphorus rich ferrite) and low (low phosphorus ferrite) hardness. The results of tensile tests show that microstructure plays a major part in determining mechanical properties. In particular, while tensile strength is improved when high hardness constituents predominate, ductility requires an optimal composite microstructure. This is discussed in relation to the deformation and fracture behaviour of the alloys, by means of an extensive fracto graphic analysis. The results of fatigue testing show that the alloy Fe–0·7C–0·8P, characterised by a predominantly pearlitic microstructure, has a lower fatigue limit than the alloy Fe-0·25C–0·6P which is predominantly ferritic, although the former has a higher tensile strength. In addition, the scatter of the fatigue tests has been analysed and shown to correlate with that of the static tests which, in previous work, has been shown to depend on the microstructural characteristics. PM/0609
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