Low temperature deformation and fracture mechanisms in nickel aluminide-iron alloys with and without yttrium(2) oxygen(3) additions

Alloys based upon the ordered intermetallic compound, NiAl, exhibit a number of favorable material properties which have made them candidate materials for advanced aerospace applications. However, application of these alloys has been confronted by two critical limitations: (1) poor low temperature ductility and fracture resistance and (2) poor high temperature creep strength. The current work has attempted to address both of these limitations through compositional control (to enhance low temperature ductility and toughness) and through oxide dispersion strengthening (to impart creep strength). The program is based on two alloy compositions: Ni-35Al-12Fe and Ni-35Al-20Fe (all compositions being given in atomic percent).;This thesis focuses on the mechanisms which control the room temperature deformation and fracture behavior of cast and extruded and mechanically alloyed NiAl-Fe alloys. The present results show the above alloys to exhibit three critical characteristics which differentiate them from most other NiAl-based alloys: (1) compatible (i.e., crack-free) deformation to large (...