焼結タングステン細線中のバブルの幾何学的特性とその異常結晶粒成長に及ぼす影響に関する計算機実験

抄録

Scanning electron microscopic (SEM) observation is made to examine the geometry of bubbles in P/M tungsten fine wires after their secondary recrystallization is completed. The effect of the geometrical properties of bubbles on abnormal grain growth is then investigated using a Monte Carlo computer simulation technique. While bubbles, with the mean diameter of 23 nm, are present at grain boundaries with a high number density of ρ=10¹³ m⁻², the number density of bubbles inside a grain is about 5% of ρ. As the specimens are annealed, ρ decreases rapidly and thereby the mean bubble diameter increases after many small bubbles form at grain boundaries. The latter is thought to be the process of bubble formation caused by the increase in the internal pressure of potassium gas, while the former is considered to be the coarsening process of large bubbles caused by the diffusion of potassium along grain boundaries from smaller to larger bubbles. Moreover, it can be concluded from the results of the computer simulation that the final abnormal grain structure is very much influenced by the mutual positional relation between the arrays of bubbles and the potential abnormal grains, being indirectly influenced by the bubble intervals in an array, the growth of bubbles, the number of initial abnormal grains and so on.