Development of ultra high strength nano-Y2O3 dispersed ferritic steel by mechanical alloying and hot isostatic pressing

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2011-09, Vol.528 (25-26), p.7475-7483
• Main Authors: Karak, S.K., Chudoba, T., Witczak, Z., Lojkowski, W., Manna, I.
• Format: Article
• Language: English
• Subjects: Alloy development; Alloy powders; Alloy steels; Applied sciences; Dispersion hardening metals; Elasticity. Plasticity; Exact sciences and technology; Ferritic stainless steels; Ferritic steel; Hot isostatic pressing; Mechanical alloying; Mechanical properties; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Microstructure; Nanostructure; Oxide dispersion strengthening; Powder metallurgy. Composite materials; Production techniques; Scanning electron microscopy; Structural steels
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2011.06.039

► Nano-Y2O3 dispersed FeCrTiAl ferritic alloys developed by mechanical alloying. ► Over 99% density (7.32–7.38Mg/m3) achieved by hot isostatic pressing. ► Dispersion of nanometric Y2Ti2O7, Y2O3, Fe11TiY or Al9.22Cr2.78Y is uniform. ► Extremely high compressive strength, modulus, fracture toughness, hardness achieved. ► Compressive strength is 2–3 times higher with lower density than similar ODS steel. The present investigation aims to develop ultra high strength ferritic steels through consolidation of mechanically alloyed powders of 1.0wt% nano-Y2O3 dispersed 83.0Fe–13.5Cr–2.0Al–0.5Ti (alloy A), 79.0Fe–17.5Cr–2.0Al–0.5Ti (alloy B), 75.0Fe–21.5Cr–2.0Al–0.5Ti (alloy C) and 71.0Fe–25.5Cr–2.0Al–0.5Ti (alloy D) alloys (all in wt%) by hot isostatic pressing (HIP) at 600, 800 and 1000°C using 1.2GPa pressure for 1h. Following this mechano-chemical synthesis and consolidation, extensive effort has been undertaken to characterize the microstructural evolution by X-ray diffraction, scanning and transmission electron microscopy and energy dispersive spectroscopy. Mechanical properties including hardness, compressive strength, Young's modulus and fracture toughness were determined using nano-indentation and universal testing machine. The present ferritic alloys record extraordinary levels of compressive strength (2012–3325MPa), Young's modulus (230–295GPa), fracture toughness (4.6–21.8MPa√m) and hardness (15.5–19.7GPa), and measure up to 2–3 times greater strength with a lower density (∼7.4Mg/m3) than that of other oxide dispersion strengthened ferritic steels (