|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Friction Stir Welding and Processing IX
||Friction-Stir-Processing Microstructure Improvement Related to Fatigue-strength and Charpy-absorbed-Energy Increase of TIG-welded SS400 Steels
||Kazuhiro Ito, Tatsuya Okuda, Hiroki Izumi, Makoto Takahashi, Kazuyuki Kohama, Hajime Yamamoto, Hidetoshi Fujii
|On-Site Speaker (Planned)
To improve fatigue strength of high-tensile-steel welds, friction stir processing (FSP) is an effective grain-refinement technique for the topmost layer of the welds. In this study, fatigue-strength and Charpy-absorbed-energy increase was found in the tungsten inert gas (TIG)-welded SS400 plates. Fatigue life exhibited more than 5.0x106 cycles to failure, which is more than 2000% increase in comparison with those of the TIG specimens, at an applied stress amplitude of 270 MPa. Its Charpy absorbed energies exhibited about 110 J in the temperature range between -110°C and 40°C. FSP produced microstructure consisting of ultrafine eqiaxial ferrite grains beneath the TIG-welded surface. A cross-sectional TEM image indicates that an about 2 nm-thick thin layer of cementite was warped round the ultrafine ferrite grains in a certain FSP condition with low heat input. This can be attributed the related increase in fatigue strength and Charpy absorbed energy.
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