Dislocation arrays formed during creep of heat-resistant nickel alloys

Conclusions

• 1. The second stage of creep in heat-resistant nickel alloys is due to changes in their intercrystalline structure.

• 2. With the same creep rate during the entire second period, which is characteristic of heat-resistant alloys containing a moderate amount of hardening phase equally distributed in the matrix, deformation is due to the gradual propagation of individual dislocations, leading to crystalline slip.

• 3. In alloys containing a substantial quantity of hardening phase creating a field of elastic distortion the deformation develops unevenly-the second state of creep has several sections with constant but differing rates of deformation. Each section is characterized by a different mechanism of the interaction of dislocation with growing particles of the hardening phase.

• 4. The low creep rate in the first section for alloy ÉI661 is due to pinning of dislocations around particles of γ′ phase; accelerated creep in the second section is due to the higher density of mobile dislocations; proparation of dislocations prevents particles of γ′ phase from growing together into platelets in the third stage with a lower creep rate.