Evolution of strain-induced precipitates in Inconel 617B alloy and their effect on flow behavior

Strain-induced precipitation was systematically investigated in austenitic Inconel 617B superalloy (IN617B) after deformation of 0.2 true strain in its service temperature range (700-850 degrees C). The precipitation-time -temperature (PTT) curves obtained by stress relaxation experiments showed a classic C-shape with the nose temperature of 800 degrees C, and a minimum incubation period of 30 s, and the main strain-induced precipitate was M23C6 carbide. After specimens deformed at 800 degrees C to a strain of 0.2 were held between 10 and 1000 s, they underwent a second-pass strain test, during which the M23C6 precipitates evolved and influenced the flow stress; this behavior was investigated. During the nucleation, growth, and coarsening of the strain -induced precipitates, the morphology of the M23C6 particles gradually changed from spherical to polygonal with increasing size, but the precipitates always maintained their cube-on-cube orientational relationship with the austenitic matrix. During the nucleation stage before 30 s, many pre-precipitation clusters and weak static recovery softening led to low second-deformation flow stress, which persisted at approximately 630 MPa. In the precipitation growth phase before 360 s, recovery softening balanced precipitation hard-ening. The strain-induced precipitates grew larger, and they were able to pin dislocations. In addition, some complex microstructures resulting from particle collisions were observed. This resulted in the maximum rate of increase of the second deformation flow stress, which quickly reached almost 700 MPa. When the holding time was extended to 1000 s, the recovery softening effect further increased, while the M23C6 particles gradually coarsened; this weakened the increasing trend of the second deformation flow stress, which increased to only 715 MPa at 1000 s (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The strain-induced precipitation process in austenitic Inconel 617B superalloy in its service temperature range was systematically investigated. The main strain-induced precipitate was identified as M23C6 carbide, with a minimum incubation period of 30 s at 800 degrees C. The morphological evolution of the precipitates and their influence on flow stress during deformation were studied in detail.