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Title: Influence of microstructure topology on the mechanical properties of powder compacted materials
Authors: Lai, Chang Quan
Seetoh, Ian
Keywords: Engineering::Materials::Mechanical strength of materials
Issue Date: 2021
Source: Lai, C. Q., & Seetoh, I. (2021). Influence of microstructure topology on the mechanical properties of powder compacted materials. International Journal of Mechanical Sciences, 198, 106353-. doi:10.1016/j.ijmecsci.2021.106353
Journal: International Journal of Mechanical Sciences 
Abstract: Powder compaction is an important technique for fabricating engineering materials as it offers good resolution and is compatible with complex stoichiometry and geometries. It forms the basis of important manufacturing processes such as powder bed 3D printing, powder metallurgy and metal injection moulding. However, a major disadvantage is that the presence of porosity in the resultant material can lead to a drastic deterioration of its mechanical properties. To improve the stiffness and strength of these powder compacts, it is imperative to pinpoint the main cause of these weakening effects. Here, we attempt to do so by examining the mechanics of different topologies that the microstructures of powder compacted materials can adopt. General structure – property relationships were first derived for (i) compression/ stretch – dominated (CD) (ii) compression, shear and bending (CSB) and (iii) compression, shear and joint rotation (CSR) topologies, for the range of relative densities between 0 and ~ 0.9. Using the Face-Centered Cubic (FCC), Body-Centered Cubic (BCC) and 3D Anti-Tetrachiral (3ATC) geometries to represent the CD, CSB and CSR topologies respectively, the analytical and simulated relative stiffness vs. relative density and relative strength vs. relative density trends were compared against experimental data in the literature. It was found that the mechanical properties of powdered materials typically fall within an exclusive range of values exhibited by the 3ATC lattice, which is much lower than that expected of FCC and BCC lattices. A closer examination of the analytical equations indicated that the low modulus of 3ATC lattices and powder compacted materials is caused by joint (i.e. particulate) rotation, while their weak strength is the result of thin beams, which manifest as narrow neck-like interparticle connections in powder compacted materials. These results are supported by previous studies, which showed that powder compacted materials have eccentric microstructures similar to 3ATC unit cells and the compression of granular material usually results in extensive particulate rotations. Higher coordination number of the particles is expected to reduce these rotations, thus illuminating the strategy for improving the modulus of powder compacted materials. The material strength, on the other hand, has already been shown to improve with a thickening of the neck regions, which can be achieved through higher sintering temperature, compressive pressure and/ or longer compaction time.
ISSN: 0020-7403
DOI: 10.1016/j.ijmecsci.2021.106353
Rights: © 2021 Elsevier Ltd. All rights reserved. This paper was published in International Journal of Mechanical Sciences and is made available with permission of Elsevier Ltd.
Fulltext Permission: embargo_20230522
Fulltext Availability: With Fulltext
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