About this Abstract |
| Meeting |
MS&T26: Materials Science & Technology
|
| Symposium
|
New Frontiers in Physical Metallurgy of Steels
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| Presentation Title |
Flow-Curve Constitutive Behavior and DIC-Measured Fracture Ductility of Automotive Sheet Steels: Voce Model Superiority and Microstructure-Driven Fracture Strain Ranking in DDQ, DP780, DP980, and TRIP590 |
| Author(s) |
Ahmed Nabil Elalem, Amirkeyvan Rahimi, Yara Almubarak |
| On-Site Speaker (Planned) |
Amirkeyvan Rahimi |
| Abstract Scope |
The plastic flow behavior and fracture ductility of four automotive sheet steels — DDQ (single-phase ferrite), DP780 and DP980 (ferrite–martensite), and TRIP590 (ferrite–bainite–retained austenite) — were characterized via quasi-static uniaxial tension (15 specimens, ASTM E8/E8M). Three constitutive hardening models (Hollomon, Swift, Voce) were ranked by RMSE: the Voce saturation model achieved lowest RMSE across all specimens (47–82% improvement over Hollomon), consistent with its physical basis in dislocation density saturation relevant to martensite-constrained and transformation-hardening microstructures. Digital image correlation captured local fracture true strains inaccessible to conventional extensometry, yielding a microstructure-driven ductility ranking spanning nearly one order of magnitude: TRIP590 (εₑ = 1.62) > DDQ (0.94) > DP780 (0.36) > DP980 (0.19). Local strains exceeded global elongation by 2–6× in DDQ and TRIP590, confirming extensometry substantially underestimates ductility. The superior ductility of TRIP590 is attributed to sustained transformation plasticity (γ→αʹ), absent in ferritic and dual-phase steels. |