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Published in:
2013 | OriginalPaper | Chapter
7. Low Nickel Maraging Steel
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Abstract
The kinetics of precipitate formation are analysed using the Johnson–Mehl–Avrami (JMA) theory. Nano-sized precipitates are formed homogeneously during the ageing process, which results in high hardness. As the ageing time is prolonged, precipitates grow and hardness increases. As-forged Fe-12.94Ni-1.61Al-1.01Mo-0.23Nb (wt%) steel has mixed ductile and brittle fracture and has good toughness. Relationships among heat treatment, microstructure and mechanical properties are discussed. Austenitisation with lower temperature and intercritical annealing are introduced in the treatment of the maraging steel. Intercritical annealing treatments do not increase hardness either before or after ageing. The impact toughness in aged condition is enhanced after austenitisation at 950 °C. Reverted austenite is suspected after austenitisation at 950 °C followed by ageing at 600 °C.