Effects of thermal aging on mechanical properties and microstructures of an interstitial high entropy alloy with ultrasonic surface mechanical attrition treatment

In this work, indentation tests have been carried out on the surface of an interstitial high-entropy alloy, which is treated with ultrasonic surface mechanical attrition treatment and thermal aging treatment at 400 °C. We present and discuss these two treatments on the mechanical behavior of the material by using flat indentation method. Meanwhile, changes in its microscopic morphology, grain size, phase structure, etc. are investigated using X-ray diffraction, electron backscatter diffraction, etc. and its microstructure evolution mechanism under the long-term high temperature condition is revealed. Flat indentation tests and microstructural investigations reveal that the mechanical behavior of interstitial high entropy alloy is significantly affected by surface mechanical attrition treatment and thermal aging time. The gradient refined and strengthened surface layers are demonstrated to appreciably upgrade the mechanical performance of interstitial high entropy alloy, while thermal aging treatment will lead to a reduction of mechanical performance and a phase transformation.