Co-evolution of point defects and Cr-rich nano-phase in binary Fe-20 at.% Cr alloy: A comprehensive investigation using positron annihilation spectroscopy and atom probe tomography
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| Format: | Preprint |
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2022
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| _version_ | 1866910323289620480 |
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| author | Sarkar, Sudip Kumar Maheshwari, Priya Pujari, P. K. Biswas, Aniruddha |
| author_facet | Sarkar, Sudip Kumar Maheshwari, Priya Pujari, P. K. Biswas, Aniruddha |
| contents | The role of point defects in temporal evolution of Cr-rich alpha-prime phase separation in binary Fe-20 at.% Cr alloy is elucidated by intercepting the long term (upto 1000 h at 773 K) aging at regular intervals and probing by a combination of atom probe tomography (APT) and positron annihilation spectroscopy (PAS). Since the Cr concentration of nano-scale α/ phase in Fe-20 at.% Cr alloy increases continually on aging, the point defects play active role throughout the aging duration. The near-atomic resolution of APT and self-seeking ability of positrons towards point defects make this analysis possible. The difference of positron affinities between Fe and Cr enables identification of the Cr-rich nano-phases that are specifically associated with defects; they would otherwise be indiscernible in the absence of defect. Thus, the temporal evolution of Cr-rich nano-phase along with the associated point defects can be fully characterized at each stage of aging using APT and PAS, respectively. The combined APT-PAS study shows that Cr-rich alpha-prime precipitation is preceded by vacancy-Cr complexes that act as nucleation sites for Cr clusters, which in turn, cause an early rise in micro-hardness due to cluster hardening. Interestingly, this is accompanied by a significant rise in point defect concentration. Our results depict that the vacancies present in the core of the alpha-prime precipitates migrate towards the precipitates interface during the course of aging and eventually get recovered resulting in virtually defect-free precipitates. This study chronicles the way the point defects shape the process of alpha-prime phase separation throughout the entire length of aging. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2205_03434 |
| institution | arXiv |
| publishDate | 2022 |
| record_format | arxiv |
| spellingShingle | Co-evolution of point defects and Cr-rich nano-phase in binary Fe-20 at.% Cr alloy: A comprehensive investigation using positron annihilation spectroscopy and atom probe tomography Sarkar, Sudip Kumar Maheshwari, Priya Pujari, P. K. Biswas, Aniruddha Materials Science The role of point defects in temporal evolution of Cr-rich alpha-prime phase separation in binary Fe-20 at.% Cr alloy is elucidated by intercepting the long term (upto 1000 h at 773 K) aging at regular intervals and probing by a combination of atom probe tomography (APT) and positron annihilation spectroscopy (PAS). Since the Cr concentration of nano-scale α/ phase in Fe-20 at.% Cr alloy increases continually on aging, the point defects play active role throughout the aging duration. The near-atomic resolution of APT and self-seeking ability of positrons towards point defects make this analysis possible. The difference of positron affinities between Fe and Cr enables identification of the Cr-rich nano-phases that are specifically associated with defects; they would otherwise be indiscernible in the absence of defect. Thus, the temporal evolution of Cr-rich nano-phase along with the associated point defects can be fully characterized at each stage of aging using APT and PAS, respectively. The combined APT-PAS study shows that Cr-rich alpha-prime precipitation is preceded by vacancy-Cr complexes that act as nucleation sites for Cr clusters, which in turn, cause an early rise in micro-hardness due to cluster hardening. Interestingly, this is accompanied by a significant rise in point defect concentration. Our results depict that the vacancies present in the core of the alpha-prime precipitates migrate towards the precipitates interface during the course of aging and eventually get recovered resulting in virtually defect-free precipitates. This study chronicles the way the point defects shape the process of alpha-prime phase separation throughout the entire length of aging. |
| title | Co-evolution of point defects and Cr-rich nano-phase in binary Fe-20 at.% Cr alloy: A comprehensive investigation using positron annihilation spectroscopy and atom probe tomography |
| topic | Materials Science |
| url | https://arxiv.org/abs/2205.03434 |