Quantifying the Degree-of-Sinter in Ferrous P/M Materials

摘要

Improvements in the physical and mechanical properties of pressed and sintered ferrous materials are made during the sintering process. Particle bonding and alloying by diffusion occur during sintering with property enhancements resulting as the sintering time is increased. The effects of sintering are visible as changes in microstructural features, such as particle boundaries and pore edges. Some of the improvements in sintering appear as a loss in particle boundaries, smoother pore edges, and a lessening in the number of angular features between particles. The appearance of these features and characteristics, in conjunction with their frequency of occurrence, is often referred to as degree-of-sinter. Quantification of the degree-of-sinter can be performed on properly prepared metallographic specimens using well-understood stereological practices. Three test methods will be discussed as techniques for quantifying and separating materials sintered to varying degrees. Additionally, images of an iron-copper-carbon premix, sintered at varying times, will be used to illustrate these microstructural changes.