On the Dynamic Mechanical Behavior of Wrought and AM 17-4 Precipitation-Hardenable Stainless Steels Under Rapid Heating

Published

May 6, 2024

Author(s)

Steven P. Mates, Saadi Habib, James Zuback, Fan Zhang

Abstract

Dynamic metal plasticity problems often involve large strains that can increase temperatures to levels sufficient to induce microstructural transformations except for the very short time-at-temperature. In these problems, dynamic mechanical behavior can become time-dependent owing to the evolving microstructural state. Precipitation reactions are an important class of transformations that can create time-dependent dynamic behavior in alloys subject to rapid heating and loading conditions. This work explores the dynamic behavior of a precipitation-hardenable stainless steel (17-4) produced by wrought and Additive Manufacturing (AM) methods with a rapidly-heated Kolsky bar technique. Wrought 17-4 is examined in three common heat treatments (solution-treated, peak-aged and over-aged) to explore the effect of the initial aging condition on the dynamic behavior for temperatures up to 1000 °C and heating times limited to ≈ three seconds. Solution-treated wrought 17-4 is observed to thermally-harden at aging temperatures (> 400 °C) due to rapid precipitate growth, becoming as strong as peak-aged material above 550 °C even under rapid heating. Strengthening of the solution-treated material and decreasing age hardening effects with increased temperature in peak-aged material, including rapid over-aging, combine to explain this result. Over-aged wrought 17-4 differs from the other two heat treatments at all temperatures, exhibiting steady thermal softening over the entire temperature range. Stress-relieved AM 17-4 exhibits high room-temperature strength and high strain hardening due to a large meta-stable austenite content. A plasticity model is developed for wrought, solution-treated 17-4 to explore and quantify the effect of rapid-age hardening on its dynamic stress-strain response. The model includes time-dependent strengthening using age-hardening kinetics data and that also accounts for temperature- and strain-dependent precipitate strengthening. The model predicts age-hardening effects on the dynamic stress-strain behavior as a function of temperature and time up to the peak-aged condition. A separate model for over-aged wrought 17-4 is also presented that considers the material to be stable with respect to aging effects at all temperatures.

Citation

International Journal of Mechanical Sciences

Pub Type

Journals

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Keywords

Kolsky Bar, Additive Manufacturing, Hybrid Manufacturing, High Strain Rate, High Heating Rate

Citation

Mates, S. , Habib, S. , Zuback, J. and Zhang, F. (2024), On the Dynamic Mechanical Behavior of Wrought and AM 17-4 Precipitation-Hardenable Stainless Steels Under Rapid Heating, International Journal of Mechanical Sciences, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936659 (Accessed May 19, 2024)