INFLUENCE OF HOT ISOSTATIC PRESSING ON MICROSTRUCTURES AND PROPERTIESOF NIAL CR(MO)-TIC IN-SITU MULTIPHASE COMPOSITES/

A novel in-situ multiphase NiAl-based composite was investigated on it s microstructures and properties influenced by HIP treatment. In the a s- processed composites, a fine array of NiAl precipitates was found t o be distributed in Cr(Mo) phase. TiC particles tended to segregate at grain or phase boundaries. In addition, a number of dislocations were observed to exist in NiAl grains meanwhile fewer in Cr(Mo) grains. Li ttle change in the morphology was found except that nearly fully densi fication was achieved. Some changes in microstructures were notable in cluding coarsening of NiAl precipitates in Cr(Mo) phase and increase i n dislocation density in NiAl phase. After HIP, the strength of the co mposites increased significantly compared with the as-processed compos ites. The reason for the enhanced strength of the composites is also d iscussed.