14th International Conference on Shot Peening

Effects of Advanced Mechanical Surface Treatments on Residual Stress, Microstructure and Mechanical Properties of a FeMnCoCrSiCu High Entropy Alloy

Anurag Sharma, Priyanka Agrawal, Saurabh S. Nene, Seetha R. Mannava, Rajiv S. Mishra and Vijay K. Vasudevan

Rivian, Normal, IL 61761, U.S.A; anurag.mse@gmail.com Department of Materials Science and Engineering, University of North Texas, Denton, TX 76207, USA; rajiv.mishra@unt.edu Department of Mechanical and Materials Science Engineering, University of Cincinnati, Cincinnati, OH 45221, U.S.A; vijay.vasudevan@unt.edu

Abstract

The effects of Laser Shock Peening (LSP) and Ultrasonic Nanocrystal Surface Modification (UNSM) on the residual stress, mechanical properties and near-surface microstructure of an FCC-based HEA alloy Fe38.5Mn20Co20Cr15Si5Cu1.5 were studied. High surface compressive residual stress (RS) of ~1,750 MPa induced by UNSM significantsly exceeded the yield strength of the base material. This can be attributed to the formation of nano-crystalline structure/grain size reduction, deformation-induced transformation and high dislocation density in the near-surface region. LSP also led to a high surface compressive RS with compression depth twice that from UNSM. Nano-indentation depth profile revealed near-surface hardness increase of ~42% with UNSM and ~27% with LSP. Hybrid peening combining LSP and UNSM was also explored which showed the cumulative effect of severe plastic deformation from UNSM and resulting high-pressure shockwaves from LSP induced high surface CRS and deeper compression depth in the material. The microstructural changes induced by these treatments were studied by XRD, EBSD/OIM and TEM and changes in the mechanical properties were assessed via tensile tests. These results will be presented and discussed in terms of their influence on the hardness and tensile properties.