اتصال آلياژ آنتروپي بالاي CoCrFeMnNi به فولاد زنگ‌نزن 316L به روش فاز مايع گذرا و ارزيابي خواص اتصال

The dissimilar joining of high-entropy alloys to other alloys is of significant importance due to cost reduction an‎d critical applications in industries such as aerospace, medical, nuclear, an‎d oil an‎d gas. In this research, dissimilar joining was achieved through a transient liquid phase process between the FeCoCrNiMn HEA an‎d 316L stainless steel, an‎d its optimal parameters were investigated. Following the preparation stages, the samples were joined using a BNi-2 interlayer at a constant temperature of 1060°C for durations of 5, 15, 30, an‎d 60 minutes under a vacuum atmosphere, followed by cooling to ambient temperature in the same atmosphere. After joining, the samples were wire-cut, an‎d prepared an‎d optimized for optical an‎d scanning electron microscopy microstructure analysis, hardness testing, an‎d corrosion eva‎luation. Shear strength tests were performed, an‎d X-ray Diffraction analysis was conducted on the samples to determine the chemical composition of the phases. Based on the obtained results, various regions were observed in the joint zone at different holding times, including isothermal solidification, non-isothermal solidification, an‎d diffusion-affected zones. Microstructural examination using optical microscopy revealed that with increasing holding time, the thickness of the non-isothermal solidification zone decreased, attributed to the reduction of intermetallic compounds. At a holding time of 60 minutes, complete isothermal solidification occurred. The non-isothermal solidification zone contained nickel an‎d chromium-rich boride compounds, as well as nickel-rich silicides. In contrast, only a nickel-rich γ solid solution phase was observed in the isothermal solidification zone, with a chemical composition closely resembling that of the initial interlayer. Shear strength test results indicated an increase in shear strength with an increase in process time, reaching a maximum value of approximately 469 MPa at 60 minutes. Fracture surface analysis suggested brittle fracture in samples with a non-isothermal solidification zone an‎d ductile fracture in joints with an isothermal solidification zone. Microhardness test results showed that the highest hardness, observed in the sample joined at 1060°C for 5, corresponded to the non-isothermal solidification zone. To eva‎luate the corrosion behavior of the samples, potentiodynamic polarization tests were performed. The results demonstrated that the sample joined at 1060°C for 60 minutes exhibited superior corrosion resistance compared to the base metals prior to joining.

مسعود عطاپور , محمد رضايت

علي اشرفي , علي شفيعي