Effect of various factors on the recovery and recrystallization of a nickel-base heat-resistant alloy

Conclusions

• 1. Disappearance of excess point defects in heat-resistant nickel alloy KhN65VMTYu begins with heating to 100° and ends at ∼250°.

• 2. A substantial change in the polygonal structure is observed with heating to 750–850°. Improvement of the intragranular structure continues in the process of secondary recrystallization — up to 1160–1180°.

• 3. Primary recrystallization begins at 900–950° and ends at 980–1020°, depending on the extent of preliminary cold working.

• 4. The temperature dependence of secondary recrystallization depends to a considerable extent on the temperature at which dispersed phases go into solution. The rate of secondary recrystallization obeys a parabolic rule. Increasing the temperature and the extent of hot deformation slightly increases the susceptibility to secondary recrystallization. The optimal recrystallization annealing treatment for the OA heat is 1180° for 2–3 h, and 1160° for 2–3 h for the OI heat.

• 5. Differences in grain size in microvolumes with ε > ε_cr are affected mainly by uneven distribution of dispersed phases.

• 6. Lowering the forging temperature leads to quite uneven deformation through the bulk of the forging and substantial differences in grain size in macrovolumes; the optimal final forging temperature is 1160°.