Abstract
This article examines contacting by means of ultrasonic welding between a cast aluminum winding and a copper conductor of a wheel hub drive for a passenger car. The effect of thermal stress on the formation and growth of intermetallic phases (IMC) in the contact is analyzed. By using microscopy, the growth constant under the specific load conditions can be identified with the help of the parabolic time law and offer a possibility for predicting the service life of the corresponding contacts. As a result, it can be stated that the increase in electrical resistance of the present contact at load temperatures of 120 °C, 150 °C, and 180 °C does not reach a critical value. The growth rates of the IMC also show no critical tendencies at the usual operating temperatures (120 °C and 150 °C, e.g., at 150 °C = 4.59 × 10−7 μm2/s). The activation energy calculated using the Arrhenius plot of 155 kJ/mol (1.61 eV) can be classified as high in comparison to similar studies. In addition, it was found that future investigations of the IMC growth of corresponding electrical contacts should rather be carried out with electric current. The 180 °C sample series were carried out in the oven and with electric current; the samples in the oven did not show clear IMC, while the samples exposed to electric current already showed IMC under the microscope.
Published Version
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