Minimizing Defects Between Adjacent Foils in Ultrasonically Consolidated Parts

Two types of defects normally occur in ultrasonically consolidated parts: (i) Defects that occur between mating foils in successive layers (“type 1” defects) and (ii) defects that occur within a layer between two foils laid side-by-side (“type 2” defects). While some success has been achieved in minimizing type 1 defects, type 2 defects, however, have been given very little attention. Both types of defects are undesirable and should be minimized if ultrasonically consolidated parts are to be used in structural applications. This work describes an investigation of how to minimize type 2 defects in ultrasonically consolidated parts. According to our hypothesis, a foil being deposited must overlap the adjacent deposited foil by an optimum amount to ensure a defect-free joint between the two foils. Transverse tensile specimens were fabricated with various amounts of foil overlap (by changing the foil width setting) to test this hypothesis. Metallographic and fractographic studies showed a clear correlation between foil overlap, defect incidence, and tensile strength. It was found that a foil width setting of 23.81 mm helps minimize type 2 defects in ultrasonically consolidated Al 3003 parts using standard foils of 23.88 mm (equivalent to 0.94 in.) nominal width.