• Isakov, Matti
• Langi, Veera
• Rubio Ruiz, Rafael Arturo
• Hokka, Mikko
• Pun, Lalit

Abstract

<p>In this work, in-situ high-energy X-ray diffraction was used to analyze the effects of strain rate and austenite (γ) grain orientation on the strain-induced martensitic transformation in metastable austenitic stainless steel 301LN. The diffraction measurements were carried out at strain rates ranging from 10⁻³ s⁻¹ to 1 s⁻¹ continuously without interrupting the experiment and thus creating nearly adiabatic conditions at the highest studied strain rate. The results indicate that &lt;100&gt;γ fiber-oriented grains preferentially transform at the strain rate of 10⁻³ s⁻¹ when the true strain is above 0.10, whereas the &lt;111&gt;γ fiber-oriented grains transform only at later stages of plastic deformation. The phase transformation rate of the &lt;111&gt;γ and &lt;100&gt;γ fiber-oriented grains decreases with increase in strain rate. A theoretical model based on stacking fault width as a function of external stress and temperature (stacking fault energy) was used to predict lower-bound estimates for the critical tensile stress needed to start ε-martensite and α’-martensite phase transformations. The model can predict the experimentally observed phase transformation behavior of the &lt;111&gt;γ fiber orientations at all strain rates but is unable to predict the decrease of phase transformation rate of &lt;100&gt; fiber-oriented γ grains with increase in strain rate, which could be related to change in dislocation structure.</p>

Topics

• impedance spectroscopy
• polymer
• grain
• stainless steel
• phase
• x-ray diffraction
• experiment
• dislocation
• stacking fault