The influence of particle size on the densification kinetics of tungsten powder during spark plasma sintering was investigated. The densification rate of tungsten powder in the intermediate sintering stage decrease with increasing particle size, resulting in a delay in the sintering stages of coarse powder. The isothermal densification kinetic behaviors of tungsten powder show that the densification of tungsten powder can be divided into two kinetic stages: a low-stress exponent segment (n = 1.5) and a high-stress exponent segment (n = 3 or 4). With increasing of particle size, n increases from 3 to 4, and the activation energy decreases from 304 to 254 kJ/mol for the high-stress exponent segment. This is because the densification mechanism has a tendency to change from diffusion creep to dislocation creep or dislocation glide as the particle size increases. The evolution of the activation energy exactly matches the transformation of the deformation mechanism, indicating that the densification activation energy does not reflect a barrier to densification, but rather a barrier to deformation with different deformation mechanisms.

研究了粒度对火花等离子体烧结过程中钨粉致密化动力学的影响。钨粉末在中间烧结阶段的致密化速率随粒度的增加而降低，从而导致粗粉烧结阶段的延迟。钨粉的等温致密化动力学行为表明，钨粉的致密化可分为两个动力学阶段：低应力指数段（n  = 1.5）和高应力指数段（n  = 3或4）。随着粒径的增加，n对于高应力指数段，它从3增加到4，活化能从304 kJ / mol减少到254 kJ / mol。这是因为随着粒径的增大，致密化机制具有从扩散蠕变变为位错蠕变或位错滑动的趋势。活化能的演化与变形机理的转变完全匹配，表明致密化活化能不反映致密化的障碍，而是反映不同变形机理的变形的障碍。