Change in kinetics of sintering under the action of ultrasonic vibration

Summary

• 1. The presence of a threshold amplitude A_t has been established, beginning from which there are observed differences in the sintering of samples subjected to the action of USV.

• 2. The threshold amplitude A_t is decreased with increase in temperature of sintering and initial porosity of the samples.

• 3. The difference in the kinetics of sintering for “sonic” and “unsonic” samples decreases with increase in “activity” of the sintered samples.

• 4. The activation energy found from the graph relating log A_t with 1/T agrees with the activation energy for self-diffusion.

• 5. The acceleration of sintering under the action of USV is accompanied by the appearance of a fine block structure which may correspond to a decreased distance between the sources and sinks for vacancies and, in this way, an increase in rate of the processes of self-diffusion.

• 6. In porous samples obtained by evaporation of Zn from brass (where there is practically no influence of USV on the rate of sintering), and in cast samples of copper after the action of USV at high temperatures, there is observed no refinement of the blocks.

• 7. In pressings of mixtures of powders of mutually diffusing metals (Cu+Ni), under the action of USV, heterodiffusion is accelerated and the growth effect caused by this developed more intensively and is completed more rapidly.