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Mina Dehghan,Reza Miresmaeili,Mohsen Askari‑Paykani,Hamid Reza Shahverdi 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.5
A novel severe plastic deformation is carried out on a medium Mn advanced high strength steel (AHSS) at both room andcryogenic temperatures which is called surface mechanical impact treatment (SMIT). After characterization, utilizing thedesign of experiment (DOE) program, it is obtained that how the SMIT parameters including time, voltage, and, shot diameteraffect the tensile test results of SMITed samples at room temperature (RT-SMITed). Microhardness profiles of SMITedsamples at cryogenic temperature (CT-SMITed) show more increase in microhardness than RT-SMITed ones up to thecenter of specimens. Additionally, the yield strength of CT-SMITed and RT-SMITed samples increases by 84% and 28% onaverage, respectively. The formation of mechanical twins, slip bands and, rhombic blocks improve both the microhardnessand yield strength of treated samples. The ultimate tensile strength (UTS) of all treated specimens decreases sharply (35%in RT-SMITed and 32% in CT-SMITed samples). According to DOE results, UTS has a negative correlation with voltageand based on fracture surface images, brittle fracture configurations increases with increasing voltage. The reason for thisobservation could be the precracks formed due to the deformation of detected MnS precipitates and the possibility of themartensite phase cracking during the SMIT process.