Metals and Materials International ( IF 3.3 ) Pub Date : 2021-07-30 , DOI: 10.1007/s12540-021-01007-5 Mina Dehghan 1 , Reza Miresmaeili 1 , Mohsen Askari-Paykani 1 , Hamid Reza Shahverdi 1
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A novel severe plastic deformation is carried out on a medium Mn advanced high strength steel (AHSS) at both room and cryogenic temperatures which is called surface mechanical impact treatment (SMIT). After characterization, utilizing the design of experiment (DOE) program, it is obtained that how the SMIT parameters including time, voltage, and, shot diameter affect the tensile test results of SMITed samples at room temperature (RT-SMITed). Microhardness profiles of SMITed samples at cryogenic temperature (CT-SMITed) show more increase in microhardness than RT-SMITed ones up to the center of specimens. Additionally, the yield strength of CT-SMITed and RT-SMITed samples increases by 84% and 28% on average, respectively. The formation of mechanical twins, slip bands and, rhombic blocks improve both the microhardness and 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 voltage and based on fracture surface images, brittle fracture configurations increases with increasing voltage. The reason for this observation could be the precracks formed due to the deformation of detected MnS precipitates and the possibility of the martensite phase cracking during the SMIT process.
Graphic Abstract
中文翻译：
一种新型严重塑性变形方法对中锰高级高强度钢显微组织和力学特性的影响
在室温和低温下对中等 Mn 高级高强度钢 (AHSS) 进行新的严重塑性变形，称为表面机械冲击处理 (SMIT)。表征后，利用实验设计（DOE）程序，获得了包括时间、电压和注射直径在内的SMIT参数如何影响SMITed样品在室温下（RT-SMITed）的拉伸试验结果。SMITed 样品在低温 (CT-SMITed) 下的显微硬度曲线显示，在样品中心处，显微硬度比 RT-SMITed 增加更多。此外，CT-SMITed 和 RT-SMITed 样品的屈服强度分别平均提高了 84% 和 28%。机械双胞胎、滑带和，菱形块提高了处理样品的显微硬度和屈服强度。所有处理过的样品的极限拉伸强度 (UTS) 急剧下降（RT-SMITed 样品中为 35%，CT-SMITed 样品中为 32%）。根据美国能源部的结果，UTS 与电压呈负相关，根据断口图像，脆性断口结构随着电压的增加而增加。这种观察的原因可能是由于检测到的 MnS 析出物的变形而形成的预裂纹以及在 SMIT 过程中马氏体相开裂的可能性。脆性断裂结构随着电压的增加而增加。这种观察的原因可能是由于检测到的 MnS 析出物的变形而形成的预裂纹以及在 SMIT 过程中马氏体相开裂的可能性。脆性断裂结构随着电压的增加而增加。这种观察的原因可能是由于检测到的 MnS 析出物的变形而形成的预裂纹以及在 SMIT 过程中马氏体相开裂的可能性。
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