About this Abstract |
Meeting |
Superalloys 2021
|
Symposium
|
Superalloys 2021
|
Presentation Title |
Dynamic and Post-dynamic Recrystallization during Supersolvus Forging of the New Nickel-based Superalloy – VDM Alloy 780 |
Author(s) |
Juhi Sharma, Masood Hafez, Bodo Gehrmann, Charbel Moussa, Nathalie Bozzolo |
On-Site Speaker (Planned) |
Juhi Sharma |
Abstract Scope |
The need of developing new high temperature materials has increased significantly in the last decades owing to the demand of higher aerospace engine operating temperatures. This requires improved microstructural stability of the polycrystalline nickel-based superalloys used for turbine disks. The microstructure of VDM Alloy 780 consists of ??′ strengthening precipitates in addition to the needle/plate-shaped particles (of ä and/or ç phase) to pin the grain boundaries. The present article aims at discussing the recrystallization behavior of the new VDM Alloy 780 in the supersolvus domain. Both dynamic and post-dynamic microstructural evolutions are reported. The dynamic recrystallization (DRX) kinetics was found to be rather sluggish. For a plastic strain of 1.3 at 1050 °C applied at a strain rate of 0.01 s-1, the microstructure of VDM Alloy 780 is only 50 % recrystallized. The DRX grain sizes are quite close for the two applied strain rates - 0.01 s-1 and 0.1 s-1. Despite slow DRX kinetics, the fast post-dynamic evolutions allowed to achieve fully recrystallized microstructures with a grain size of 26 ìm within 5 minutes of post-deformation holding at 1050 °C. The post-dynamically recrystallized grain sizes were predominantly temperature dependent and were not sensitive to strains and strain rates within the applied range. Deformation followed by 5 minutes holding at temperatures below 1050 °C but still in the single phase domain could eventually generate finer grain sizes (< 20 ìm). The low sensitivity of the grain size obtained after post-dynamic evolution to the applied strain and strain rates is an advantage for the industrial forging routes wherein the deformation conditions can vary over the piece. Another advantage of this alloy is the relatively slow grain growth kinetics which makes possible to obtain homogenous and reasonably fine microstructures after supersolvus forging. |
Proceedings Inclusion? |
Undecided |