ON THE PRIMARY η-PHASE IN A HIGH-Ti Ni-Fe-Cr BASED SUPERALLOY

The precipitation and dissolution together with their control of the primary η-phase in ahigh-Ti Ni-Fe-Cr base superalloy have been investigated.The precipitation of primaryη-phase was found to be closely related to Ti or Al content and solidification rate of the alloy.The aggregation of blocky η-phase may remarkably reduce the tensile strength,ductility andrupture life of the alloy.The temperature-time relation of dissolution of the primary η-phaseobeys T=1370-86.1 lgt for as-cast superalloy.The formation of primary η-phase may beprevented by the reasonable control of Ti or Al content and smelting process.The adoption oftreatment under large hot deformation and homogenization may be the remedy forunfavorable influence of η-phase.