Gradient nanostructure and residual stresses induced by Ultrasonic Nano-crystal Surface Modification in 304 austenitic stainless steel for high strength and high ductility

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:613

Article

Ye, Chang¹  Telang, Abhishek²  Gill, Amrinder S.²  Suslov, Sergey³  Idell, Yaakov⁴  Zweiacker, Kai⁴  Wiezorek, Joerg M. K.⁴  Zhou, Zhong⁵  Qian, Dong⁵  Mannava, Seetha Ramaiah²  Vasudevan, Vijay K.² 

[1] Univ Akron, Dept Mech Engn, Akron, OH 45325 USA

[2] Univ Cincinnati, Dept Mech & Mat Engn, Cincinnati, OH 45221 USA

[3] Purdue Univ, Sch Mat Engn, W Lafayette, IN 47906 USA

[4] Univ Pittsburgh, Dept Mech Engn & Mat Sci, Pittsburgh, PA 15261 USA

[5] Univ Texas Dallas, Dept Mech Engn, Richardson, TX 75080 USA

关键词: Ultrasonic Nano-crystal Surface;    Modification (UNSM);    Deformation twins;    Gradient microstructure;    Residual stresses;    Fatigue performance;    Precession electron diffraction (PED);   

DOI  :  10.1016/j.msea.2014.06.114

来源: Elsevier

【 摘 要 】

In this study, the effects of Ultrasonic Nano-crystal Surface Modification (UNSM) on residual stresses, microstructure changes and mechanical properties of austenitic stainless steel 304 were investigated. The dynamic impacts induced by UNSM leads to surface nanocrystallization, martensite formation, and the generation of high magnitude of surface compressive residual stresses (-1400 MPa) and hardening. Highly dense deformation twins were generated in material subsurface to a depth of 100 mu m. These deformation twins significantly improve material work-hardening capacity by acting both as dislocation blockers and dislocation emission sources. Furthermore, the gradually changing martensite volume fraction ensures strong interfacial strength between the ductile interior and the two nanocrystalline surface layers and thus prevents early necking. The microstructure with two strong surface layers and a compliant interior embedded with dense nanoscale deformation twins and dislocations leads to both high strength and high ductility. The work-hardened surface layers (3.5 times the original hardness) and high magnitude of compressive residual stresses lead to significant improvement in fatigue performance; the fatigue endurance limit was increased by 100 MPa. The results have demonstrated that UNSM is a powerful surface engineering technique that can improve component mechanical properties and performance. (C) 2014 Elsevier B.V. All rights reserved.

【 授权许可】

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