Particle size evolution of V-4Cr-4Ti powders in high energy vibrating and planetary ball milling

In a current research, V-4Cr-4Ti alloy powders were prepared by high energy vibrating balling and planetary ball milling, respectively. X-ray diffraction (XRD) and Rietveld refinement were employed to estimate dislocations density and grain size of ball milled powder. Scanning electron microscopy (SEM) was used to characterize the morphologies of alloy powder. The results show that dislocation density of planetary ball milled powder was much lower than vibrating ball milling at similar input energy. Based on the researches of particle size, dislocation density and grain size, ball milling process of V alloy powder could be described as two basic stages, initial stage and final stage. At initial stage, input energy was absorbed by the increase of dislocation density and fine grains; accordingly, in final stage, input energy was absorbed by powder cracking. The initial stage in planetary ball milling lasts much longer. The development of particle size was highly affected by ball size because of the difference of critical energy for plastic deformation. Another result based on this critical energy was that high energy ball milling could not be replaced by accumulation of long-time ball milling at relatively low energy. Besides, the evolution of microstructure was highly correlated with ball to powder rate (BPR).