Abstract

Ni-20Cr-20Fe-5Nb alloy with or without Y_2O_3 was manufactured by mechanical alloying process and consolidated by spark plasma sintering (SPS). The grain size of the alloy with Y_2O_3 was smaller than that of alloy without Y_2O_3 which results from the effect of Y_2O_3 suppressing grain growth. The tensile strength at room temperature was increased by the addition of Y_2O_3 but decreased abruptly at temperature above 600°C. It seems to result from the change of deformation mechanism due to fine grain size, that is, grain boundary sliding is predominant at above 600°C while internal dislocation movement is predominant at below 600°C. After conventional heat treatment process of solution treatment and aging, a small amount of delta(Ni_3Nb) phase was formed in Ni-20Cr-20Fe-5Nb alloy while a large amount of gamma"(Ni_3Nb) was formed in Inconel 718 in the previous report. This is due to exhaustion of Nb content by the formation of NbC during consolidation.

• Keywords: Mechanical alloying;ODS alloy;Inconel 718;