DETAILED LINKAGES OF POWDER CHARACTERISTICS TO PROPERTIES IN PRESS- SINTER PROCESSING OF POWDER METALS

Discrete element analysis is used to map particle size distributions into measures of the pore size distribution after die filling up to sintering. A surprising outcome is the ability to map the pore size distribution as a means to link with fracture-based properties, from just the density and particle size distribution. Combinations evaluated using the technique include monosized powders, bimodal mixtures, and various log-normal distributions. The latter proves most relevant to press-sinter powder metallurgy by providing a mapping of the starting particle size distribution into property predictions. The results show the formation of large pores in die filling that need to be avoided to ensure high sintered properties. With this approach, insight is gained on those aspects of the initial particle size distribution that limit sintered properties. Hence, it is possible to anticipate property limits such as fatigue life or fracture toughness since large pores initiate fracture and provide a short-circuit failure path in fatigue. Recommendations are made for how particle size shifts are required to ensure the highest possible mechanical properties for less than full-dense press-sinter compacts