Effect of oxygen contents on predominant sintering mechanism during initial stage of pure titanium powder

This study investigates the sintering neck growth behavior of pure titanium powder with different oxygen contents. The growth rate of the sintering neck gradually decreased as the oxygen content increased from 0.06 wt% to 0.50 wt%. At the same time, it was observed that the oxygen in the sintering neck spread to the low oxygen region as the size of the neck increased. A theoretical analysis indicated that surface diffusion is the dominant diffusion mechanism. However, under the hindrance of oxygen in the matrix, both surface diffusion and grain boundary diffusion slow down. Calculating the increase in the self-diffusion activation energy of Ti atoms indicated that oxygen was more resistant to surface diffusion. Predictably, grain boundary diffusion will become the dominant diffusion mechanism in the initial stage of sintering when the oxygen content exceeds 2.628 wt%.