Evolution of nano-sized precipitates in δ-ferrite of high-Cu CF8M with thermal aging and their stability against reversion heat treatment
The aim of this study was to investigate the evolution of thermal aging-induced nano-sized precipitates in δ-ferrite of high-Cu CF8M cast austenitic stainless steel (CASS) and the stability of these precipitates against reversion heat treatment (R-HT). The CF8M was subjected to thermal aging at 400 ...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2025-05-01
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| Series: | Journal of Materials Research and Technology |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2238785425012906 |
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| Summary: | The aim of this study was to investigate the evolution of thermal aging-induced nano-sized precipitates in δ-ferrite of high-Cu CF8M cast austenitic stainless steel (CASS) and the stability of these precipitates against reversion heat treatment (R-HT). The CF8M was subjected to thermal aging at 400 °C for up to 20,000 h. Initially, thermal aging stimulated spinodal decomposition of δ-ferrite accompanied by the formation of Cu-rich clusters, G-phase and omega (ω) phase precipitates. The spinodal decomposition and secondary phase precipitates further evolved with the increase in thermal aging duration to 20,000 h. The Cu-rich clusters remained either as coherent BCC Cu precipitate adjacent to the G-phase or as part of G-phase and did not transformed to other structures, even after long-term thermal aging as well as after R-HT at 550 °C for 1 h. The R-HT of aged CF8M lead to the dissolution of spinodal decomposition and desegregation of Ni in δ-ferrite. However, despite the desegregation of Ni, G-phase and ω-phase precipitates exhibited minimal dissolution after R-HT demonstrating greater thermal stability. The size, number density and volume fraction of G-phase and ω-phase precipitates in δ-ferrite were determined for both aged and R-HTed conditions. These microstructural changes in δ-ferrite of CF8M could be correlated with the hardening of δ-ferrite after thermal aging and the subsequent reduction in hardness after R-HT. |
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| ISSN: | 2238-7854 |