Warm Formability of 0.2 Pct C-1.5 Pct Si-5 Pct Mn Transformation-Induced Plasticity-Aided Steel

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2017-05, Vol.48 (5), p.2237-2246
• Main Authors: Sugimoto, Koh-ichi, Hidaka, Shin-nosuke, Tanino, Hikaru, Kobayashi, Junya
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Formability; Forming; Martensite; Martensitic transformations; Materials Science; Matrix; Metallic Materials; Nanotechnology; Punching; Retained austenite; Stabilization; Steel; Structural Materials; Structural steels; Surfaces and Interfaces; Temperature; Thin Films; TRIP steels
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-017-4046-5

The warm stretch formability and flangeability of 0.2 pct C-1.5 pct Si-5 pct Mn transformation-induced plasticity-aided sheet steel with annealed martensite matrix were investigated for automotive applications. Both formabilities were enhanced by warm forming at peak temperatures of 423 K to 573 K and 423 K to 523 K (150 °C to 300 °C and 150 °C to 250 °C), respectively. The superior warm formabilities were mainly due to the stabilization of a large amount of retained austenite by warm forming and the consequent considerably suppressed void growth at the interface between the matrix and transformed martensite, despite there being large hole punching damage for the stretch flangeability. High peak temperatures for stretch formability and flangeability were associated with apparently increased M S of the retained austenite resulting from the increased mean normal stress on stretch forming and hole expansion.