Enhanced thermoplasticity of 7Mo-0.4 N contained super austenitic stainless steel through pre-deformation

This study investigated the hot tensile deformation behavior of super austenitic stainless steel (SASS) with different pre-deformation degrees within 1150-1250'C. The influence of pre-deformation on the number of annealing twin (AT), grain size, dislocation evolution, sigma phase precipitation, static recrys-tallization (SRX), and dynamic recrystallization (DRX) behaviors at hot tensile deformation stages is ana-lyzed. Results show that the thermoplasticity of the SASS increases first and then decreases with the increase of pre-deformation degree at each deformation temperature. The area reduction of the samples pre-deformed for 0 %, 10 %, 20 %, and 25 % are 0.25, 0.32, 0.37, and 0.35, respectively at a tensile temper-ature of 1150r. When the pre-deformation degree is within the range of 0-20 %, the deformation storage energy (DSE) gradually increases with the pre-deformation degree. The SRX amount at the high -temperature holding stage and the DRX amount in the high-temperature deformation stage significantly increases, and the grain size gradually decreases. As a result, crack initiation and propagation are inhib-ited, and thermoplasticity improves. However, when the pre-deformation degree is increased to 25 %, the grains grow abnormally during the high-temperature tensile deformation, and a large number of sigma phases are induced, which deteriorates the thermoplasticity of the SASS.(c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).