Investigation of Floating and Single-Action Dies in Producing Dense Compacts with High Aspect Ratio
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RESEARCH PAPER
Investigation of Floating and Single‑Action Dies in Producing Dense Compacts with High Aspect Ratio H. Homayoun1 · M. Shahbaz2 · R. Ebrahimi1 Received: 13 August 2018 / Accepted: 17 June 2019 © Shiraz University 2019
Abstract In this study, the commercially pure aluminum powder was compacted by single-action and floating dies at room temperature. The effect of compaction method on densification was studied using density distribution, microhardness measurements and scanning electron microscope (SEM) along the compaction axis of processed samples. The density measurements of compacted samples through the floating die process shows more uniform density distribution in comparison with singleaction process, which is in good agreement with microhardness and SEM results. Results also show that the densification requires lower compaction load in floating die process than is needed in single-action compaction process, which is due to the improvement of the frictional condition by making change in relative movement in the frictional surfaces of floating die process. Therefore, it makes floating die more beneficial in producing dense compacts with high aspect ratio (ratio of height to diameter) which is not possible in single-action die compaction process. Keywords Aluminum powder · Single-action compaction · Floating die compaction · Density distribution · Microhardness
1 Introduction The powder metallurgy (PM) is one of the manufacturing methods of industrial parts (Kumar et al. 2015; Mavhungu et al. 2017; Ramakrishnan 2013). It consists of a controlled blending of metal powders, compacting the resulted mixture in an appropriate die and then sintering (Angelo and Subramanian 2008; Moreno and Oliver 2011). Compacting in a die step consists of pressing the powder contained in the die cavity by applying pressure with one or more punches in a stationary or movable die. Relative motion between die and powder in die cavity introduces interface friction that besides its effect on the expenditure of energy in overcoming friction, it affects the quality of the compact by controlling the uniformity of pressing pressure and then density distribution through the compact (Michrafy et al. 2004). In the single-action compaction process, the lower punch and die are both stationary and the pressing pressure * M. Shahbaz [email protected] 1
Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz, Iran
Department of Materials Science and Engineering, School of Engineering, Urmia University, Urmia, Iran
2
is applied by an upper movable punch. Interface friction causes non-uniform distribution of density in the green compact which reduces along the compaction axis by moving toward the lower stationary punch. After compacting, the green compact is ejected from the die cavity by the movement of the lower punch. In this process, in the presence of interface friction, the green compact will be produced by high aspect ratio but with low and non-uniform distributed density (
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