In the current research, there is high interest in nanocrystalline iron and chromium based alloys. The iron-chromium has long been used by many engineering alloys as basis in high-strength and corrosion-resistant applications such as for fuel cell interconnect. The problem is there is high crystalline growth at high temperature operation up to 1000 0C. Therefore, this research investigates the crystallite size and solid solubility of the Fe80Cr20 metallic material that projected have high thermal stability to applied as Interconnect fuel cell. The method of this research was conducted through high energy milling for 60 h and ultrasonic bath by frequency of 35 kHz and various holding time of 3, 3.5, 4, 4.5 and 5 h. The analysis of the crystallite size and solid solubility were conducted by X-Ray Diffraction (XRD) with diffraction angle of 10-900 and operation time of 25 minutes. High energy ball milling is the most effective technique to reduce the crystallite size up to 96 % and it combined with ultrasonic achieve 2.171 nm crystallite size and improve the solid solubility up to 86.4 % as compared to the raw material. These results achieved high energy kinetics and the ball slugging the powder during ball milling process.