Influence of microstructure topology on the mechanical properties of powder compacted materials

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 mo...

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Main Authors: Lai, Chang Quan, Seetoh, Ian
Other Authors: Temasek Laboratories @ NTU
Format: Article
Language:English
Published: 2021
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Online Access:https://hdl.handle.net/10356/146719
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-1467192021-03-13T20:11:54Z Influence of microstructure topology on the mechanical properties of powder compacted materials Lai, Chang Quan Seetoh, Ian Temasek Laboratories @ NTU Engineering::Materials::Mechanical strength of materials Particles Lattices 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. Ministry of Defence (MINDEF) Accepted version Funding for this project was provided by C.Q.L.’s Temasek Research Fellowship, for which he gives thanks. 2021-03-08T07:12:04Z 2021-03-08T07:12:04Z 2021 Journal Article 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 0020-7403 https://hdl.handle.net/10356/146719 10.1016/j.ijmecsci.2021.106353 198 106353 en International Journal of Mechanical Sciences © 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. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Engineering::Materials::Mechanical strength of materials
Particles
Lattices
spellingShingle Engineering::Materials::Mechanical strength of materials
Particles
Lattices
Lai, Chang Quan
Seetoh, Ian
Influence of microstructure topology on the mechanical properties of powder compacted materials
description 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.
author2 Temasek Laboratories @ NTU
author_facet Temasek Laboratories @ NTU
Lai, Chang Quan
Seetoh, Ian
format Article
author Lai, Chang Quan
Seetoh, Ian
author_sort Lai, Chang Quan
title Influence of microstructure topology on the mechanical properties of powder compacted materials
title_short Influence of microstructure topology on the mechanical properties of powder compacted materials
title_full Influence of microstructure topology on the mechanical properties of powder compacted materials
title_fullStr Influence of microstructure topology on the mechanical properties of powder compacted materials
title_full_unstemmed Influence of microstructure topology on the mechanical properties of powder compacted materials
title_sort influence of microstructure topology on the mechanical properties of powder compacted materials
publishDate 2021
url https://hdl.handle.net/10356/146719
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