Diffusion welding of an RS/PM aluminum alloy

A methodology was devised for optimizing diffusion welding parameters for an RS/PM Al-9Fe-4Ce alloy. Temperature-time and temperature-pressure bonding parameter zones developed for the alloy using short-term coarsening studies showed that it was possible to perform diffusion welding operations on the alloy at temperatures up to 600 C (1112 F) without structural support. The bonding parameter zones were useful in limiting microstructural coarsening and consequent softening of the alloy during diffusion welding operations with silver electroplated interlayers. Joint efficiencies up to 70% were obtained with increased specimen deformation (i.e. combined deformation and diffusion welding). Bonds consisted of Ag{dollar}sb2{dollar}Al type binary intermetallic layers surrounded by complex quarternary intermetallic layers. Kirkendall porosity was found to limit joint-strengths in all specimens. In specimens that experienced no deformation during bonding, the porosity promoted separation at the interface between the base material and the intermetallic layers. Bond-strengths increased with increasing deformation during bonding. Specimen geometries that permitted higher bonding pressures without increasing specimen deformation during bonding were not found to suppress or heal the porosity. Non-wetting of the base material surfaces by eutectic liquid formed with an electroplated silver layer resulted in poor transient-liquid phase bonds between the Al-Fe-Ce alloy specimens.