Shiraz University Iranian Journal of Materials Forming 2383-0042 12 4 2025 10 01 Hot Deformation Behavior of an API X70 Steel: A Processing Map Approach 20 33 8284 10.22099/ijmf.2025.53864.1341 EN Fatemeh Ahmadi Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran Mohsen Reihanian Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran Mostafa Eskandari Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran Seyed Reza Alavi Zaree Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran Journal Article 2025 08 01 This study investigates the hot deformation behavior of an API X70 microalloyed steel using a processing map approach. Cylindrical specimens were subjected to compression tests at temperatures ranging from 950 to 1100 °C and strain rates from 0.001 to 1 s⁻¹. Flow curves revealed typical features of work hardening, dynamic recovery, and dynamic recrystallization. Power dissipation efficiency and instability criteria were calculated using a dynamic material model to construct processing maps at various strain levels. The maps identified three optimal hot deformation regions at higher strains, with the most favorable zone (efficiency of 25–33%) located at 1075–1100 °C and 0.001–0.005 s⁻¹. Microstructural validation confirmed these safe zones, while unstable regions were characterized by crack formation and deformation bands. A constitutive analysis yielded an apparent activation energy for hot deformation of 572.5 kJ/mol. The findings provide valuable guidance for optimizing hot working conditions of API X70 steel. https://ijmf.shirazu.ac.ir/article_8284_81a4506efb20b0890bddde226c22a4a3.pdf