You would like to develop a new polycrystalline Ni alloy for

You would like to develop a new polycrystalline Ni alloy for Boeing aircraft engines. The Ni parts will be under a constant stress of about 50 MPa due to centrifugal forces, and a temperature of about 1100 Which creep mechanisms are you most concerned about in this application? List at least two metallurgical/processing techniques that are employed to enhance the creep resistance of metal alloys.

Solution

a) Here dislocation glide is the dominant mechanism of deformation. This is NOT creep, so I’m not worried about designing a microstructure that is particularly resistant to lattice or gb diffusion, and I’d want to include in my microstructure any strengthening mechanisms that would increase the resistance to dislocation glide (e.g., solute atoms, grain boundaries via grain size reduction, work hardening via prior plastic deformation to increase dislocation density). However, since I know the next-fastest mechanism around this temp/stress is dislocation creep, I would also design the microstructure to reduce lattice diffusion (increase QL), potentially by adding solute atoms.

b)

Three metallurgical/processing techniques that are employed to enhance the creep resistance of metal alloys are

(1)solid solution alloying,

(2) dispersion strengthening by using an insoluble second phase

(3) increasing the grain size or producing a grain structure with a preferred orientation.