Density Gradients Formed during Compaction of Bronze Powders: the Origins of Part-to-Part Variation

摘要

The existence of density gradients in metal compacts has been recognized for over 50 years. However, previous attempts to quantify these gradients were limited by the difficulty of the technique involved and the ambiguity of the results. In this article, the utility of X-ray computer tomography (XRCT) in providing quantitative characterization of part-to-part variation in bronze compacts is demonstrated. Compaction behavior was also contrasted with previous work on porous spray-dried agglomerates. The density distribution patterns are qualitatively and quantitatively dissimilar. Different mechanisms appear to dominate the transmission of stress through assemblies of solid metal particles vs that of "softer," spray-dried agglomerates. In addition, XRCT reveals that the structures found in the so-called "loose" powder (or "fill") prior to compaction are both more complex than previously believed and capable of influencing final part-to-part variation.