The microstructure of a dissimilar AA2024 - Cu linear friction joint is investigated at a fine scale.

A phenomenological mechanism of material flow is proposed.

Al₂Cu, AlCu, Al₂Cu₃, Al₄Cu₉ as well as two metastable phases are identified.

The interfacial zone presents ideal crystallographic shear texture components.

The intermetallic compounds are harmful for the tensile properties of the joint.