Compaction behavior of Al6061 powder in the semi-solid state

Semi-solid powder processing involves compaction of metallic alloy powders in temperature ranges when both solid and liquid phases coexist. However, modeling of such process has been very scarce. In this study, compaction behavior of Al6061 powder in the presence of liquid phase was investigated. The relationship between compaction pressure and relative density of powder in the semi-solid state was modeled and verified against experimental measurements. The results showed that the powder compaction behavior can be accurately predicted by Shima–Oyane model when the liquid fraction was below 20%. In this range, all the normalized pressure–relative density curves merged into one, which could be expressed in a simple exponential form. When the liquid fraction was higher than 20%, the model failed to predict the compaction behavior because of the non-uniform distribution of the liquid phase. Squeezing-out of the liquid phase and interlocking of the irregular solid phase were speculated to occur during the compaction process.

Graphical abstractCompaction of Al6061 powder in the semi-solid state was analyzed and modeled. Compaction behavior was different based on the liquid fraction (fl). All normalized compaction curves merged into a single exponential equation when 0 < fl < 20%.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights►Closed die powder compaction in semi-solid state was modeled for the first time. ►Change in structural response occurred around liquid fraction (fl) of 10%. ►Model accurately predicted compaction behavior when fl was below 20%. ►All normalized compaction curves merged into a single exponential equation. ►Model failed when fl > 20% due to liquid phase agglomeration and squeeze-out.