Effect of PWHT on the Microstructure and Mechanical Properties of Friction Stir Welded DP780 Steel
In the present study, the effect of post-weld heat treatment (PWHT) on the microstructure and mechanical properties of friction stir welded (FSW) DP780 steel sheets was investigated. FSW was carried out at a constant tool rotation speed of 400 rpm and different welding speeds (200 mm/min and 400 min...
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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/2075-4701/11/7/1097 |
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| author | Umer Masood Chaudry Seung-Chang Han Fathia Alkelae Tea-Sung Jun |
| author_facet | Umer Masood Chaudry Seung-Chang Han Fathia Alkelae Tea-Sung Jun |
| author_sort | Umer Masood Chaudry |
| collection | DOAJ |
| description | In the present study, the effect of post-weld heat treatment (PWHT) on the microstructure and mechanical properties of friction stir welded (FSW) DP780 steel sheets was investigated. FSW was carried out at a constant tool rotation speed of 400 rpm and different welding speeds (200 mm/min and 400 min/min). A defect free weld was witnessed for both of the welding conditions. The mutual effect of severe plastic deformation and frictional heat generation by pin rotation during the FSW process resulted in grain refinement due to dynamic recrystallization in the stir zone (SZ) and thermo-mechanically affected zone (TMAZ). Lower tensile elongation and higher yield and ultimate tensile strengths were recorded for welded-samples as compared to the base material (BM) DP780 steel. The joints were subsequently annealed at various temperatures at 450–650 °C for 1 h. At higher annealing temperature, the work hardening rate of joints gradually decreased and subsequently failed in the softened heat-affected zone (HAZ) during the uniaxial tensile test. Reduction in yield strength and tensile strength was found in all PWHT conditions, though improvement in elongation was achieved by annealing at 550 °C. The digital image correlation analysis showed that an inhomogeneous strain distribution occurred in the FSWed samples, and the strain was particularly highly localized in the advancing side of interface zone. The nanoindentation measurements covering the FSWed joint were consistent with an increase of the annealing temperature. The various grains size in the BM, TMAZ, and SZ is the main factor monitoring the hardness distribution in these zones and the observed discrepancies in mechanical properties. |
| first_indexed | 2024-03-10T09:32:35Z |
| format | Article |
| id | doaj.art-9ce1621ff59640bf92fd2b13a17a7a95 |
| institution | Directory Open Access Journal |
| issn | 2075-4701 |
| language | English |
| last_indexed | 2024-03-10T09:32:35Z |
| publishDate | 2021-07-01 |
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| series | Metals |
| spelling | doaj.art-9ce1621ff59640bf92fd2b13a17a7a952023-11-22T04:23:46ZengMDPI AGMetals2075-47012021-07-01117109710.3390/met11071097Effect of PWHT on the Microstructure and Mechanical Properties of Friction Stir Welded DP780 SteelUmer Masood Chaudry0Seung-Chang Han1Fathia Alkelae2Tea-Sung Jun3Department of Mechanical Engineering, Incheon National University, Incheon 22012, KoreaDepartment of Mechanical Engineering, Incheon National University, Incheon 22012, KoreaDepartment of Mechanical Engineering, Incheon National University, Incheon 22012, KoreaDepartment of Mechanical Engineering, Incheon National University, Incheon 22012, KoreaIn the present study, the effect of post-weld heat treatment (PWHT) on the microstructure and mechanical properties of friction stir welded (FSW) DP780 steel sheets was investigated. FSW was carried out at a constant tool rotation speed of 400 rpm and different welding speeds (200 mm/min and 400 min/min). A defect free weld was witnessed for both of the welding conditions. The mutual effect of severe plastic deformation and frictional heat generation by pin rotation during the FSW process resulted in grain refinement due to dynamic recrystallization in the stir zone (SZ) and thermo-mechanically affected zone (TMAZ). Lower tensile elongation and higher yield and ultimate tensile strengths were recorded for welded-samples as compared to the base material (BM) DP780 steel. The joints were subsequently annealed at various temperatures at 450–650 °C for 1 h. At higher annealing temperature, the work hardening rate of joints gradually decreased and subsequently failed in the softened heat-affected zone (HAZ) during the uniaxial tensile test. Reduction in yield strength and tensile strength was found in all PWHT conditions, though improvement in elongation was achieved by annealing at 550 °C. The digital image correlation analysis showed that an inhomogeneous strain distribution occurred in the FSWed samples, and the strain was particularly highly localized in the advancing side of interface zone. The nanoindentation measurements covering the FSWed joint were consistent with an increase of the annealing temperature. The various grains size in the BM, TMAZ, and SZ is the main factor monitoring the hardness distribution in these zones and the observed discrepancies in mechanical properties.https://www.mdpi.com/2075-4701/11/7/1097DP780 steelFSWmicrostructuremechanical propertiesmicrohardnessnanoindentation |
| spellingShingle | Umer Masood Chaudry Seung-Chang Han Fathia Alkelae Tea-Sung Jun Effect of PWHT on the Microstructure and Mechanical Properties of Friction Stir Welded DP780 Steel Metals DP780 steel FSW microstructure mechanical properties microhardness nanoindentation |
| title | Effect of PWHT on the Microstructure and Mechanical Properties of Friction Stir Welded DP780 Steel |
| title_full | Effect of PWHT on the Microstructure and Mechanical Properties of Friction Stir Welded DP780 Steel |
| title_fullStr | Effect of PWHT on the Microstructure and Mechanical Properties of Friction Stir Welded DP780 Steel |
| title_full_unstemmed | Effect of PWHT on the Microstructure and Mechanical Properties of Friction Stir Welded DP780 Steel |
| title_short | Effect of PWHT on the Microstructure and Mechanical Properties of Friction Stir Welded DP780 Steel |
| title_sort | effect of pwht on the microstructure and mechanical properties of friction stir welded dp780 steel |
| topic | DP780 steel FSW microstructure mechanical properties microhardness nanoindentation |
| url | https://www.mdpi.com/2075-4701/11/7/1097 |
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