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A nickel-based superalloy is examined during monotonic deformation at cryogenic temperatures, reaching as low as liquid helium temperature. A detailed multimodal analysis of the microstructure and plasticity is conducted to discern changes in deformation mechanisms and plastic deformation localization under cryogenic conditions. This study employs high-resolution digital image correlation to identify the deformation mechanisms and understand their influence on plastic deformation localization as the temperature varies. At cryogenic temperatures, unusual plastic deformation localization processes are observed, attributed to the competing activation of a range of deformation processes. Furthermore, a mechanism of slip delocalization, i.e., local plastic deformation homogenization through closely spaced slip, is noted at these extreme temperatures. Ultimately, the impact of the microstructure is identified across the temperature range, from room to cryogenic temperatures.
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Investigation of Thermomechanical Coupling in Inconel 718 at Homologous Temperatures of 0.2 and 0.5
A study was conducted to investigate the temperature dependence of thermomechanical coupling in Inconel 718 (IN718). IN718 was selected as a model material due to deformation being predominantly accommodated by planar slip. Split-Hopkinson (or Kolsky) tension bar experiments were conducted at a nominal strain rate of 750 s^-1 at room temperature and 450 ^o C, representing homologous temperatures (T_H=T/T_melt) of T_H = 0.2 and T_H = 0.5, respectively. During deformation, specimen gauge sections were imaged with a high-speed infrared camera. Using one-dimensional wave analysis, the transient heat conduction equation, and temperature- dependent specific heat capacity values, the temperature rise as a function of plastic strain was used to calculate plastic work, thermal work, and the plastic work to heat conversion efficiency, commonly known as the Taylor–Quinney coefficient (TQC). As expected, a significant reduction in plastic work was observed during testing at elevated temperatures. The temperature rise due to plastic deformation was observed to be lower at room temperature compared to elevated temperature experiments. It is reported here for the first time that the TQC is a temperature-sensitive quantity. At T_H = 0.5, a nearly complete conversion of plastic work to heat was observed (TQC = 1.0). Under ambient conditions of T_H = 0.2, a much lower efficiency TQC = 0.4 was observed.
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- Award ID(s):
- 1847653
- PAR ID:
- 10537938
- Publisher / Repository:
- Springer
- Date Published:
- Journal Name:
- Metallurgical and Materials Transactions A
- Volume:
- 55
- Issue:
- 9
- ISSN:
- 1073-5623
- Page Range / eLocation ID:
- 3591 to 3600
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/s11661-024-07492-8
