Processing and characterization of diffusion-bonded Al-Si interfaces

Aluminum/silicon/aluminum sandwich specimens were produced via diffusion bonding in high vacuum at 843 K for 1 h with an applied pressure of 1.5M Pa in a uni-axial die. Details of process conditions and surface preparation of Si and Al for optimal bonding are discussed and rationalized. Following diffusion bonding, the morphology, texture, and chemistry of the interfacial region were examined using optical, scanning electron microscopy, orientation imaging microscopy, and transmission electron microscopy (TEM). It was found that the aluminum immediately adjacent to the interface underwent intense plastic deformation and recrystallization, helping to break up the native oxide layer. TEM revealed the presence of a thin O-rich amorphous layer at the interface. The interface between the Si and the amorphous layer was sharp, whereas, on the Al side, the amorphous region gradually transitioned to crystalline Al. The amorphous layer is thought to arise as a result of the native oxide layer that exists on Al prior to diffusion bonding.