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

Chang Ye, Abhishek Telang, Amrinder S. Gill, Sergey Suslov, Yaakov Idell, Kai Zweiacker, Jörg M.K. Wiezorek, Zhong Zhou, Dong Qian, Seetha Ramaiah Mannava, Vijay K. Vasudevan

Research output: Contribution to journalArticle

127 Citations (Scopus)

Abstract

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. μm. 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.

Original languageEnglish
Pages (from-to)274-288
Number of pages15
JournalMaterials Science and Engineering A
Volume613
DOIs
Publication statusPublished - 8 Sep 2014

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Keywords

  • Deformation twins
  • Fatigue performance
  • Gradient microstructure
  • Precession electron diffraction (PED)
  • Residual stresses
  • Ultrasonic nano-crystal surface modification (UNSM)

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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