Nano AlN Effect on W-Cu Composite Material Density and Hardness

By experiment, we can find that with the increasing AlN, W-Cu composite density tends to decrease. Theoretical density reduction is due to the low density of AlN itself (3.26g / cm3), which is much less than that of tungsten and copper. So with the increase of AlN content, the theoretical density of the whole material decreases naturally. While the measured density decrease is not only because of the low density of AlN itself, it also includes from relative density: one is the addition of nano AlN particles hinders the rearrangement of tungsten particles, which the tungsten copper material densification in liquid sintering depends on. The higher the content of nano-AlN particles, the more obvious the blocking effect, the more difficult the rearrangement of tungsten particles, the more difficult to fill the pores; the other is the wetting ratio of AlN particle is not as good as W and Cu at high temperature, so the addition will decrease the density of tungsten copper composite materials. In a word, few nano AlN particles have no effect on W-Cu composite material and it can further improve physical and mechanical properties.

W-Cu composite material usually uses Brinell hardness (HB) or Rockwell hardness (HR). In accordance with the addition of AlN and hardness measurements plotting the change curve, we can clearly found that the hardness of W-Cu composite material is improved with the increasing amount of nano AlN particles, which also indicates the addition of AlN particles reduced the interfacial bonding, but it played the role of fine grain strengthening and dispersion strengthening, especially for matrix copper. However, when the content exceeds 1%, the increasing trend of hardness is slowed down, because the density of tungsten-copper composite decreases, which leads to the increase of porosity in matrix.

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