Nano-Bainitic Steels: Acceleration of Transformation by High Aluminum Addition and Its Effect on Their Mechanical Properties
Additions of 3 and 5 wt.% Al have been investigated as a low-cost method for transformation acceleration in nano-bainitic steels. For both Al contents, two groups of steels with C-content in the range ~0.7 to ~0.95 wt.% were studied. Thermodynamic and physical simulations were used in alloy and heat...
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MDPI AG
2021-07-01
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| Series: | Metals |
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| Online Access: | https://www.mdpi.com/2075-4701/11/8/1210 |
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| author | Mohamad Akram Mohamed Soliman Heinz Palkowski |
| author_facet | Mohamad Akram Mohamed Soliman Heinz Palkowski |
| author_sort | Mohamad Akram |
| collection | DOAJ |
| description | Additions of 3 and 5 wt.% Al have been investigated as a low-cost method for transformation acceleration in nano-bainitic steels. For both Al contents, two groups of steels with C-content in the range ~0.7 to ~0.95 wt.% were studied. Thermodynamic and physical simulations were used in alloy and heat treatment design. Characterization was performed via dilatometry, scanning and transmission electron microscopy, Synchrotron X-ray diffraction, and tensile and impact testing. Fast bainitic-transformation time-intervals ranging from 750–4600 s were recorded and tensile strengths up to 2000 MPa at a ductility of ~10 elongation percent were attainable for the 3 wt.% Al group at an austempering temperature of 265 °C. Higher Al additions were found to perform better than their lower Al counterparts as the austempering temperature is dropped. However, Al lowered the austenite stability, increased the martensite start temperature, austenitization temperatures and, consequently, the prior austenite grain size, as well as limiting the austempering temperatures to higher ones. Additionally, the lowered austenite stability coupled with higher additions of hardenability elements (here carbon) to maintain the martensite start at around 300 °C, causing the 5 wt.% Al group to have a large amount of low stability retained austenite (and consequently brittle martensite) in their microstructure, leading to a low elongation of around 5%. |
| first_indexed | 2024-03-10T08:36:13Z |
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| id | doaj.art-78b523ac205f4e5396f70cf8a58a1585 |
| institution | Directory Open Access Journal |
| issn | 2075-4701 |
| language | English |
| last_indexed | 2024-03-10T08:36:13Z |
| publishDate | 2021-07-01 |
| publisher | MDPI AG |
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| series | Metals |
| spelling | doaj.art-78b523ac205f4e5396f70cf8a58a15852023-11-22T08:41:06ZengMDPI AGMetals2075-47012021-07-01118121010.3390/met11081210Nano-Bainitic Steels: Acceleration of Transformation by High Aluminum Addition and Its Effect on Their Mechanical PropertiesMohamad Akram0Mohamed Soliman1Heinz Palkowski2Institute of Metallurgy, Clausthal University of Technology, 38678 Clausthal-Zellerfeld, GermanyInstitute of Metallurgy, Clausthal University of Technology, 38678 Clausthal-Zellerfeld, GermanyInstitute of Metallurgy, Clausthal University of Technology, 38678 Clausthal-Zellerfeld, GermanyAdditions of 3 and 5 wt.% Al have been investigated as a low-cost method for transformation acceleration in nano-bainitic steels. For both Al contents, two groups of steels with C-content in the range ~0.7 to ~0.95 wt.% were studied. Thermodynamic and physical simulations were used in alloy and heat treatment design. Characterization was performed via dilatometry, scanning and transmission electron microscopy, Synchrotron X-ray diffraction, and tensile and impact testing. Fast bainitic-transformation time-intervals ranging from 750–4600 s were recorded and tensile strengths up to 2000 MPa at a ductility of ~10 elongation percent were attainable for the 3 wt.% Al group at an austempering temperature of 265 °C. Higher Al additions were found to perform better than their lower Al counterparts as the austempering temperature is dropped. However, Al lowered the austenite stability, increased the martensite start temperature, austenitization temperatures and, consequently, the prior austenite grain size, as well as limiting the austempering temperatures to higher ones. Additionally, the lowered austenite stability coupled with higher additions of hardenability elements (here carbon) to maintain the martensite start at around 300 °C, causing the 5 wt.% Al group to have a large amount of low stability retained austenite (and consequently brittle martensite) in their microstructure, leading to a low elongation of around 5%.https://www.mdpi.com/2075-4701/11/8/1210nano bainitecarbide free bainiteadvanced high strength steel (AHSS)retained austenitemechanical propertiesAl content |
| spellingShingle | Mohamad Akram Mohamed Soliman Heinz Palkowski Nano-Bainitic Steels: Acceleration of Transformation by High Aluminum Addition and Its Effect on Their Mechanical Properties Metals nano bainite carbide free bainite advanced high strength steel (AHSS) retained austenite mechanical properties Al content |
| title | Nano-Bainitic Steels: Acceleration of Transformation by High Aluminum Addition and Its Effect on Their Mechanical Properties |
| title_full | Nano-Bainitic Steels: Acceleration of Transformation by High Aluminum Addition and Its Effect on Their Mechanical Properties |
| title_fullStr | Nano-Bainitic Steels: Acceleration of Transformation by High Aluminum Addition and Its Effect on Their Mechanical Properties |
| title_full_unstemmed | Nano-Bainitic Steels: Acceleration of Transformation by High Aluminum Addition and Its Effect on Their Mechanical Properties |
| title_short | Nano-Bainitic Steels: Acceleration of Transformation by High Aluminum Addition and Its Effect on Their Mechanical Properties |
| title_sort | nano bainitic steels acceleration of transformation by high aluminum addition and its effect on their mechanical properties |
| topic | nano bainite carbide free bainite advanced high strength steel (AHSS) retained austenite mechanical properties Al content |
| url | https://www.mdpi.com/2075-4701/11/8/1210 |
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