Flow softening behavior during hot compression of a Nb-Si based ultrahigh temperature alloy

The flow softening behaviors of a Nb-Si based ultrahigh temperature alloy during hot compression to height reductions of 10, 30 and 60% respectively at 1410 °C have been investigated. The flow characteristics during dynamic softening of the alloy have been revealed. The evolution of deformed microstructure during compression is that the coupled Nbss/Nb₅Si₃ eutectics have been gradually broken down accompanied by the development of continuous Nbss matrix with evenly dispersed silicide particles. The softening mechanisms of the Nb-Si based ultrahigh temperature alloy have been discussed based on the orientation variation of both Nbss and Nb₅Si₃ phases, the deformed microstructure and its flow characteristics. The softening of the alloy is mainly dominated by the continuous dynamic recrystallization (CDRX) of Nbss. The CDRX of Nb₅Si₃ has occurred at a much more sluggish rate and has just been significantly activated with the height reduction increasing from 30 to 60%. The gradual refinement of silicide particles has been observed with increase in strain.