Nano AlN Effect on W-Cu Composite Material Microstructure
Compared with surface backscattered electron topography of different AlN addition, we can found that both of W-Cu and W-Cu/AlN composite material have dense and uniform microstructure. There is a small amount of large particles on tungsten copper material surface after hot pressing sintering, which is caused by W-W connection growth. With the increasing amount of AlN, it greatly reduces the W-W contact probability, and promote the sintered particles continue to be refined. But when the amount of nano-AlN added to a certain extent, the composite material appears in the copper pool and more pores. The main reason is that AlN particle has poor wettability with Cu at high temperature, which obstructs the flowing liquid copper and causes the segregation and density decrease.
In addition, due to the agglomeration and grain growth after sintering, AlN is also large in grain size. AlN particles are all scattered in the Cu phase, because the AlN particles are added in a short time ball milling mixture, which does not reflect with the W or Cu solid interface in the matrix, and AlN has good stability, so after hot pressing sintering is still better to maintain the nature of the particles themselves.
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