Effect of Reversal Time on Tungsten Copper Powder Granularity

Analyze the effect of tungsten copper powder by changing operation cycle of high-energy planetary ball milling reversal time. Generally, the operation time of planetary ball mill machine is 1-999min, and the positive and negative reversal cycle is 1-99min. In order to achieve the best ball milling effect, the rotating speed, ball milling time, the ball (size, collection, etc), the size and amount of sample and accessories choosing are all important.

Observe tungsten copper composite powder by scanning electron microscope (SEM) in different reversal time, we can find that tungsten copper composite powder particles of irregular shape, indicating that as reducing the time change, the powder grain size smaller, and appears reunion phenomenon. The shorter reversal time, the agglomeration phenomenon of tungsten copper composite powder is more obvious. Tungsten-copper composite powder and other rolling, cold rolling and upsetting effect shaft structure, ball and ball, between the ball and the tank wall under, along with reducing the time change, tungsten, copper W-Cu powder in plastic deformation, a sheet-like composite powder is formed under cold welding. Furthermore, since the strain hardening and microscopic increase plastic composite powder decreased, resulting in its fracture refinement, the particles after fracture and constantly repeated cold welding and fracture occurs again, tungsten, copper particles are more uniformly mixed composite powder becomes even finer particles.

In the process of solid solution, a small amount of copper (Cu) diffuse into tungsten (W) phase and form solution, which enlarges the distance of crystal face. However, with the decreasing reversal time, residual stress is increasing and the distance of crystal face is decreasing. It indicates that the impact of residual stress plays a leading role in the process. This is due to the high energy ball milling process, the tungsten-copper composite powder in ball rolling, cold rolling and shearing strong process, resulting in a severe plastic deformation has great stress and strain. Within the grains formed a lot of dislocation, distortion and other microscopic defects, and increase the microscopic strain, dislocation of a large number of tangles, and to further promote the formation of sub-cellular structures and lead to reduced grain size. Meanwhile, due to a large amount of crystal defects inside the particles, the atomic activity and energy storage systems increases, which promote the formation of solid solution.

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