A Method for the Estimation of the Interface Temperature in Ultrasonic Joining

Ultrasonic joining of copper foil to 1100 aluminum sheet at nominal joining temperatures of 298 K to 413 K (25 A degrees C to 140 A degrees C) for 1.25 second caused significant copper diffusion into the aluminum sheet, indicating very high diffusivity (D) values of 1.54 x 10(-13) to 2.22 x 10(-13) m(2)/s. The D values reflect high excess vacancy concentrations caused by the rapid plastic deformation in the joining surfaces. A method is presented to estimate the actual values of interface temperature from the diffusion data and expected values of vacancy concentrations. The estimated values of interface temperature were about 390 to 410 deg below the equilibrium melting point of aluminum, and in agreement with reported experimental values.