Development of ultra high strength nano-Y2O3 dispersed ferritic steel by mechanical alloying and hot isostatic pressing
✍ Scribed by S.K. Karak; T. Chudoba; Z. Witczak; W. Lojkowski; I. Manna
- Publisher
- Elsevier Science
- Year
- 2011
- Tongue
- English
- Weight
- 1017 KB
- Volume
- 528
- Category
- Article
- ISSN
- 0921-5093
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✦ Synopsis
The present investigation aims to develop ultra high strength ferritic steels through consolidation of mechanically alloyed powders of 1.0 wt% nano-Y 2 O 3 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 1.2 GPa pressure for 1 h. 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 (2012-3325 MPa), Young's modulus (230-295 GPa), fracture toughness (4.6-21.8 MPa √ m) and hardness (15.5-19.7 GPa), and measure up to 2-3 times greater strength with a lower density (∼7.4 Mg/m 3 ) than that of other oxide dispersion strengthened ferritic steels (<1200 MPa) or tungsten based alloys (<2200 MPa). The novelty of these alloys lies in the unique microstructure comprising uniform dispersion of 20-30 nm Y 2 O 3 (ex situ) or Y 2 Ti 2 O 7 (in situ) particles in higher volume fraction in high-Cr ferritic matrix.