Particle morphology-dependent deformation mechanisms in sintered Cu structures

Abstract

Particle morphology is a critical structural variable in pressure-assisted sintering because it controls packing, pore topology, interparticle bonding and load transfer. Here, copper (Cu) was used as a model system to examine how monomodal spherical, bimodal spherical and flake-shaped particle assemblies, processed under identical conditions, form porous structures with distinct mechanical responses. Micro-pillar compression reveals low effective elastic moduli of 7.5–12.5 GPa and high yield strengths of 403–450 MPa. The deformation pathways are strongly morphology dependent. The monomodal structure accommodates strain through distributed pore collapse and particle deformation, leading to progressive densification hardening. The bimodal structure exhibits size-partitioned deformation, with large particles forming the main load-bearing backbone and smaller particles accommodating local rearrangement, embedding and shear compaction. The flake-shaped structure undergoes geometry-guided deformation, where extended face-to-face bonding enhances local load bearing, while inter-flake misalignment concentrates strain and promotes shear localization. Post-compression transmission electron microscopy (TEM) and transmission Kikuchi diffraction (TKD) analyses link these modes to pore collapse, neck deformation and grain-scale strain accommodation. TKD further gives average Geometrically Necessary Dislocations (GND) densities of 4.36×10¹⁴ m⁻², 3.69×10¹⁴ m⁻² and 4.11×10¹⁴ m⁻² for the monomodal, bimodal and flake-shaped structures, respectively. Molecular dynamics (MD) simulations reproduce the corresponding strain-localization patterns and reveal morphology-controlled load-transfer pathways dominated by Shockley partial dislocations. These results establish particle morphology as a design parameter for tuning stiffness, strength and damage tolerance in sintered porous metals.