Ultrasonic induces grain refinement in gas tungsten arc cladding AlCoCrFeNi high-entropy alloy coatings

摘要

High-entropy alloys (HEA) are promising coating and structural materials for their excellent mechanical and corrosion properties, but the problems like coarse grain hinder the application. Ultrasonic treatment generally has the effect of grain refinement. Therefore, ultrasonic treatment is introduced to the process of gas tungsten arc (GTA) cladding AlCoCrFeNi HEA coatings. It was found that under ultrasonic treatment, the average grain diameter is refined by 70% (from 285 μm to 78 μm). The microhardness is increased by 20% (from 441 HV_1 to 532 HV_1), which is mainly attributed to the Hall-Petch relation. The corrosion performance in 3.5 wt% NaCl solution is also improved and the corrosion type changed from intergranular corrosion to uniform corrosion, which is mainly attributed to the increased segregation of Cr at grain boundaries. The mechanism of the impact of ultrasonic treatment on HEA coatings is discussed based on numerical simulation. Cavitation effect and acoustic streaming play a significant role in the dendritic fragmentation and consequent grain refinement.