Neck growth kinetics during ultrasonic-assisted sintering of copper powder

The present paper presents an investigation of the neck growth kinetics during ultrasonic-assisted sintering of the loose spherical copper particles. The study was performed to identify the sintering mechanism during the initial stage sintering of the copper powder. The classical sphere-to-sphere approach was used to determine the neck growth between the particles at four different sintering temperatures 700, 800, 900 and 950 celcius at different soaking time of 60, 180, 300, 600, and 900 s. The neck growth exponent was found to be 6.21, 4.92, 5.26 and 5.13 for different sintering temperatures, respectively, which signified the involvement of surface and volume diffusion mechanism during the initial stage sintering of copper particles with ultrasonic vibration assistance. The neck growth calculation was attempted to compare with conventional sintering. The evidence of the local heating between the particles was evolved from the activation energy calculations, which was found to be lower than the conventional sintering. An attempt was made to develop a numerical model for the prediction of neck growth by considering the rise in temperature due to friction between the particles owing to ultrasonic vibrations at different sintering temperature and soaking time. The model was obtained to be in-line with the trend of the experimental results.