Strain-Rate Dependence of the Martensitic Transformation Behavior in a 10 Pct Ni Multi-phase Steel Under Compression

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 51; no. 10; pp. 5101 - 5109
• Main Authors: Lambert, P. K., Hustedt, C. J., Casem, D. T., Sinclair, N., Zhang, X. J., Lee, K. M., Leong, A. F. T., Schuster, B. E., Hufnagel, T. C.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.10.2020; Springer Nature B.V
• Subjects: Alloy steels; Austenite; Characterization and Evaluation of Materials; Chemistry and Materials Science; Deformation; Dependence; Dynamic loads; Electron backscatter diffraction; Heat treating; Heat treatment; Impact resistance; Impact strength; Low temperature; Low temperature resistance; Magnetic measurement; Martensite; Martensitic transformations; Materials Science; Metallic Materials; Nanotechnology; Nickel; Steel alloys; Strain rate; Structural Materials; Surfaces and Interfaces; Thin Films
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-020-05913-y

The deformation-induced transformation of metastable austenite to martensite can contribute to improved performance of many steel alloys in a range of applications. For example, one class of Ni-containing steels that has undergone consecutive heat treatments of quenching (Q), lamellarization (L), and tempering (T) exhibits improved ballistic resistance and low-temperature impact toughness. To better understand the origin of this improvement, we tracked the volume fraction of austenite present in a QLT 10 wt pct Ni steel during compression at low and high strain rates ( ε ˙ = 0.001 s - 1 and ε ˙ ≃ 2500 s - 1 , respectively) using ex situ vibrating sample magnetometry measurements and in situ time-resolved X-ray diffraction measurements. We observe that the austenite-to-martensite transformation occurs more readily during quasi-static loading than during dynamic loading, even at small values of applied strain, which is qualitatively different from the behavior of steels known to undergo a strain-induced martensitic transformation mechanism. We propose that the strain-rate dependence of transformation in the QLT 10 pct Ni steel is dominated by the transformation in small austenite particles, where stress-assisted martensitic transformation is likely to be the dominant mechanism. Indirect evidence for this hypothesis is provided by electron backscatter diffraction measurements of deformed specimens.