Design and Development of Low Density and Refractory Based on Ni-Ti-Al-Li-Si Pentanary Equiatomic High Entropy Alloys: Microstructure and Phase Analysis

Materials for aero-engine and structural applications require the appropriate design of alloying elements that could exhibit better properties even at elevated temperatures. High entropy alloys (HEAs) have sparked worldwide attention to develop novel alloys composed of equiatomic quinary elements (Ni–Ti–Al–Li–Si) to develop lightweight material, viz. mechanical alloying (MA) technique. MA technique is applied to synthesize the newly designed composition HEA (ball-milling process carried out at 0, 1, 10, 20, 30, 40, and 50 h). The developed alloy is subjected to various characterizations such as X-ray diffraction, scanning electron microscope, transmission electron microscope, differential scanning calorimeter, and thermogravimetric analysis. The alloy confirms the face-centered cubic crystal structure with lattice parameter a = 3.5 A° at 50 h of ball milling, and elemental mapping confirms the presence of all elements. HEA in a ball-milled state confirms the nano-crystallite size of 11.5 nm with a percent lattice strain equal to 0.6089. Thermal studies clearly show the developed alloy is stable without any phase transformation. The 50 h of ball milled Ni–Ti–Al–Li–Si alloy powder is subjected to hot compaction at 850 °C for 1 h duration. The developed alloy was tested for density examination, which resulted in an average value of 3.5 ± 0.06 g/cm 3 , which is in good agreement with a theoretical density of 3.7 g/cm 3 .