Deformation and Pulse Current Coinduced Microstructural Evolution at Al–Cu Interfaces: Mechanisms and Temperature Effects

Abstract

This work systematically investigates the critical influence of joining temperature (425–500 °C) on the interfacial microstructure and mechanical properties of Al/Cu bimetallic composites prepared via pulsed-current diffusion bonding. The results reveal that temperature nonlinearly governs interfacial evolution through a competitive mechanism involving recrystallization, diffusion, and intermetallic compound (IMC) growth. Below 450 °C, the recrystallization fraction in the Cu layer increases substantially, whereas the high-stacking-fault-energy Al layer undergoes primarily dynamic recovery. At the optimal temperature of 450 °C, a continuous and stable IMC layer (∼8.2 μm) forms, achieving a synergistic balance between Cu recrystallization and interfacial bonding. Beyond 475 °C, however, accelerated interfacial reactions lead to IMC coarsening, Kirkendall voiding, and thermal stress cracking, resulting in brittle interfacial failure. Theoretical analysis indicates that the pulse current exerts a synergistic Joule-heating and electron-wind effect, which promotes preferential atomic migration along close-packed planes and releases residual stresses, thereby facilitating an optimized interface with low dislocation density and high orientation stability. This study provides a novel strategy for achieving reliable bonding of heterogeneous materials in aerospace lightweighting and electronic packaging applications.