Densification and microstructural development of stainless steel powder compacts during hot powder vehicle compaction was investigated. The preheated powder preform, vacuum encapsuled in a borosilicate glass, was compacted in a steel die using preheated alumina granules as a pressure transmitting medium. The condition for the full-densification was determined as a function of pressure and temperature. Three microstructural features were observed during the compacting process; solutioning of dendritic structure, recrystallization and normal grain growth, which in turn was found to be mainly dependent on preheating temperature. It has been found that a submicron-sized micro-structure is formed during the recrystallization stage. The densification mechanism of the present compaction process has been discussed on the basis of a concept of pressure sintering map.
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