Microstructure-based crystal plasticity modeling of sintered nano-silver under load-controlled jump tests

Sintered nano-silver is a promising die-attach material for high-temperature power electronics, but the reliability is significantly influenced by inherent porosity. Accurately modeling the mechanical behavior requires capturing the complex interplay between its porous microstructure and viscoplastic deformation. In this work, a microstructure-based crystal plasticity finite element model (CPFEM) is developed based on realistic microstructures. To characterize the mechanical behavior under complex loading, a novel set of load-controlled jump tests, incorporating both creep holds and rapid load-rate variations, was conducted on bulk samples at 250 °C. Experimental results revealed a significant increase in the strain hardening rate at high loading velocities, which conventional constitutive models fail to capture. Therefore, a modified Voce hardening law is proposed, which introduces a new parameter allowing the asymptotic hardening rate to evolve with accumulated shear strain. The CPFEM, implementing this modified law, successfully simulated the complex creep behavior and accurately predicted the rate-dependent response of the jump tests. Simulation results confirm that voids act as significant stress concentrators, inducing highly heterogeneous local stress and plastic strain. Furthermore, the analysis reveals that the voids fundamentally alters texture evolution during compression, causing a deviation from the typical <110> fiber texture found in dense FCC materials due to the geometric necessity of grains rotating to accommodate void collapse. This work provides a validated, microstructure-based framework for understanding and predicting the complex mechanical behavior of porous sintered nano-silver.