Characterization of the mechanical and microstructural properties of cryogenic and austempering heat treatments on Mo alloyed ductile cast iron
Materials Research Express, cilt.13, sa.12, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 13 Sayı: 12
- Basım Tarihi: 2026
- Doi Numarası: 10.1088/2053-1591/ae79fa
- Dergi Adı: Materials Research Express
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chemical Abstracts Core, Compendex, INSPEC, Directory of Open Access Journals, Materials Science & Engineering Collection (ProQuest), Technology Collection (ProQuest)
- Anahtar Kelimeler: ausferritic matrix, carbide precipitation, impact toughness, martensitic transformation, phase stability
- Eskişehir Osmangazi Üniversitesi Adresli: Evet
Özet
This study examines the combined effects of molybdenum (Mo) alloying and deep cryogenic treatment (DCT) on the microstructure and mechanical response of austempered ductile iron (ADI). Ductile irons with three Mo contents (0.388, 0.671, and 0.990 wt.%) were produced, austempered at 400 °C, and subsequently subjected to DCT at −196 °C for 360 min. Microstructural and phase analyses were conducted using optical microscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and x-ray diffraction (XRD). Austempering resulted in a typical ausferritic matrix, while the subsequent cryogenic step was associated with further microstructural refinement and features indicative of partial transformation of retained austenite. In addition, fine secondary features were observed locally and attributed to carbide-like precipitates. Quantitative XRD analysis revealed the presence of α and γ reflections in all heat-treated conditions. Detailed diffraction scans exhibited a distinct peak shift toward lower 2θ angles following DCT, indicating an expansion of the lattice parameters and a corresponding enrichment of carbon within the austenite phase. In terms of mechanical response, the integration of austempering and DCT led to a 16.6% increase in hardness compared to the as-cast state. Furthermore, the combined heat treatment cycle resulted in a 42.3% enhancement in impact energy relative to the initial cast condition, highlighting the potential of DCT to optimize the structural integrity and toughness of Mo-alloyed ADI.