Effect of Ball Charge Fraction on Mechanical Alloying by a Vibratory Ball Mill-An Estimate by Two-dimensional Model Simulation-

摘要

Ball motion in a vibratory ball mill during mechanical alloying was studied by a two-dimensional model simulation to estimate an effect of ball charge fraction on the mechanical alloying process. As a result, it was found that the ball motion changed drastically at a ball charge fraction between 0.7 and 0.8. The ball motion became so violent and the power consumed by dashpots of descrete element method model increased so much in a range of high fractions. It was found from the simulation that the range of ball movement was limited to lower parts of the mill vessel at ball charge fractions less than 0.7, while the range of ball movement spread over the vessel at fractions over 0.8, which inaeased the frequency of ball-to-vessel collision and also increased energy transferred from vessel to balls. However, the amplitude and frequency of vibration and the power of actual vibratory mills must decrease with an increase in the ball charge fraction because of the limitation of driving motor power. It suggests that an effective ball charge fraction should be in a range from 0.7 to 1.0.