Processing and Properties of a Ni-ZrO2 P/M Composite

The powder metallurgy processing route is used for preparing Ni-matrix MMC by incorporating ultrafine Zr0 2 powder that is agglomerated into micron sized clusters. After blending with ball milling, the heated porous MMC is consolidated using the compression of a cam plastometer. Characterization of the MMC using SEM and EDAX reveals that most of the Zr0 2 clusters existing in the Zr0 2 feed powder can be nearly completely broken up by the ball milling process during blending. However, residual Zr0 2 clusters in a loose structure are preserved in the final sintered Ni-Zr0 2 material. After compression using a Cam plastometer, the clusters are not broken up but are flattened into discs but not densified or penetrated with Ni. A de-agglomeration process was attempted as an alternative blending process in order to achieve a better distribution of Zr0 2 . The results showed a modest improvement in the breakup of the clusters. Despite the presence of these clusters, it is shown that the dispersed Zr0 2 powders do increase activation energy for the flow stress of the MMC.