Effects of strain rate on strain-induced martensite nucleation and growth in 301LN metastable austenitic steel

Lalit Pun, Guilherme Corrêa Soares, Matti Isakov, Mikko Hokka

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The effects of strain rate on strain-induced α′-martensite nucleation and growth were analyzed in this work. Tension tests were performed at room temperature at strain rates of 2×10−4 s−1 and 0.5 s−1 using small polished specimens that fit inside a scanning electron microscope. The specimens were deformed incrementally, and microstructural evolution was tracked carefully at a specific location on the specimen surface. This approach allows the analysis not only of the spatial but also of the temporal evolution of the α′-martensite. Optical microscopy images and electron backscatter diffraction (EBSD) measurements were taken for each plastic deformation increment. The size and number of α′-martensite particles were evaluated from the EBSD images, whereas local microlevel strains were obtained using Digital Image Correlation (DIC). According to the results, the number of nucleation sites for α′-martensite does not seem to be affected much by the strain rate. However, there is a notable strain rate effect on how the transformation proceeds in the neighborhood of freshly formed α′-martensite particles. At a low strain rate, repeated nucleation and coalescence leads to the notable growth of α′-martensite particles, whereas at a high strain rate, once nucleated α′-martensite particles remain as small isolated islands that do not markedly grow with further plastic strain. This phenomenon can be attributed to local microstructure-level heating caused by plastic deformation and exothermic phase transformation. This reduces the local growth rate of the α′-martensite particles in the vicinity of the above-mentioned islands, thus leading to a lower bulk transformation rate at higher strain rates.

Original languageEnglish
Article number142218
Number of pages10
JournalMaterials Science and Engineering A
Early online date20 Oct 2021
Publication statusPublished - 13 Jan 2022
Publication typeA1 Journal article-refereed


  • Digital image correlation
  • Electron backscatter diffraction
  • Metastable austenitic stainless steel
  • Strain rate effect
  • Strain-induced α′-martensite transformation

Publication forum classification

  • Publication forum level 2

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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