Particle Morphology-dependent Microstructure and Fracture Toughness in Sintered Copper Particles

Abstract

In this study, the morphology-dependent microstructure and fracture toughness of pressure-assisted sintered copper (Cu) particles are investigated using focused ion beam scanning electron microscopy (FIB-SEM) reconstruction, transmission Kikuchi diffraction (TKD), micro-cantilever bending experiments, and molecular dynamics (MD) simulations. Three representative particle systems are examined, namely monomodal, bimodal, and flake-shaped particles. Three-dimensional FIB-SEM reconstructions show that particle morphology strongly influences densification, with porosities of approximately 13.2%, 6.7%, and 17.8% for the monomodal, bimodal, and flake-shaped systems, respectively. The bimodal particles form the most densified microstructure due to hierarchical packing, where smaller particles occupy interstitial regions between larger particles. TKD analyses further reveal morphology-dependent neck structures and grain distribution, where bimodal particles develop more continuous interparticle necks, whereas flake-shaped particles exhibit lamellar interfaces with residual interlamellar pores. Fracture toughness measurements demonstrate a strong dependence on particle morphology. The bimodal sample exhibits the highest fracture resistance, with J2% of approximately 129 J/m2 and KJ of about 3.6 MPa m1/2. The monomodal sample shows significantly lower resistance, with J2% of approximately 49 J/m2 and KJ of about 1.8 MPa m1/2. The flake-shaped sample shows an intermediate J2% value of approximately 98 J/m2, but a lower KJ of about 0.9 MPa m1/2. MD simulations further reveal that particle morphology governs strain localization, dislocation activity, and crack propagation mechanisms.