Martensite to austenite reversion in cryorolled AISI 317 L stainless steel

Resumo

© 2025 Elsevier Inc.Martensite to austenite reversion was investigated in cryorolled AISI 317 L austenitic stainless steel. The material was rolled at 77 K to a thickness reduction of 50 % and subjected to isothermal annealing for 1 h from 200 to 1100 °C, as well as continuous annealing up to 1000 °C. Austenite reversion was followed by several characterization techniques including dilatometry, differential scanning calorimetry (DSC), X-ray diffraction (XRD), Vickers microhardness testing, DC-magnetization, light optical (LOM) and scanning electron (SEM) microscopy, high-resolution electron backscatter diffraction (EBSD), energy-dispersive X-ray spectroscopy (EDS), and electron channeling contrast imaging (ECCI). Dilatometric, calorimetric and magnetization measurements show that αˈ-martensite to austenite reversion occurs within the temperature range of 400–700 °C. The reversion of ε-martensite occurs between 300 and 400 °C. In the range of 700–900 °C sigma (σ) and chi (χ) phases precipitate within δ-ferrite. Full recrystallization and dissolution of σ and χ precipitates take place around 1000 °C. After reversion, austenite has the same texture components of cryorolled state; i.e., Brass, Goss and S components. The persistent morphology of the deformation microstructure up to 700 °C, as well as few changes in texture, point to a displacive reversion mechanism. The temperature for shear-dominated reversion estimated by thermodynamic calculations is approximately 526 °C. By choosing a proper temperature window and annealing time, the reversion of martensite to austenite leads to a quasi-bimodal austenite grain size distribution, which helps overcome the tradeoff between strength and ductility.

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