Light Weight MnTiAlNiFe High-Entropy Alloy (LWHEA) Fabricated by Powder Metallurgy Process: Mechanical, Microstructure, and Tribological Properties

Abstract

The present work is focused on the development of lightweight high entropy alloy (LWHEA) using a powder metallurgy process. The primitive powders of manganese (Mn), titanium (Ti), aluminum (Al), nickel (Ni), and iron (Fe) with a purity of ∼ 99.5 % and particle size in the range of 40 to 70 µm were considered as a raw material for the synthesis of present LWHEA. The elemental powders at an equal molar ratio were mechanically alloyed (MA) in a high-energy ball milling for 28 hrs. The MA powders were then cold compacted using 500 MPa pressure, followed by sintering at 900 °C in an inert atmosphere to produce a bulk cylindrical sample of 8 mm diameter and 8 mm height. The average particle size of the milled powders was measured by FESEM image analysis, while the crystal size of the milled powders was predicted from the XRD peak broadening followed by full-width half maximum (FWHM) peak profile calculation using the Hall-Williamson method. The BCC structure, along with intermetallic phases, was identified in the sintered bulk LWHEA of MnTiAlNiFe. Some intermetallic phases act as reinforcement in the alloy. The EDX analysis of MA powder revealed that all the elemental powders were distributed homogeneously to form a solid solution of LWHEA powder. The deformation behavior of the sintered MnTiAlNiFe LWHEA was studied by analyzing the loading–unloading curve of micro indentation. A remarkable improvement in the hardness values (microhardness ∼ 7.382 GPa and Martens hardness ∼ 3.09 GPa at 3 N load) was observed compared to conventional lightweight metallic alloys. The investigation of the wear behavior of the bulk MnTiAlNiFe LWHEA samples carried out in a Universal Tribometer coupled with a 3D optical profilometer predicts the load-dependent coefficient of friction of the sample.