Seminar Title
Processing, Microstructure and Mechanical Behaviour of High Entropy Alloys Obtained by Mechanical Alloying and Vacuum Arc Melting processes
Seminar Type
Progress Seminar
Department
Metallurgical and Materials Engineering
Speaker Name
Naveen Kumar Mindi ( Rollno : 519mm1003)
Speaker Type
Student
Venue
M. Tech. Class room, MM Annex Building
Date & Time
01 Feb 2023 11:00 AM
Contact
Prof. Krishna Dutta
Abstract

High entropy alloys (HEAs) are a special class of advanced engineering materials, which constitute at least five principal elements with configurational entropy (∆𝑆𝑐𝑜𝑛𝑓) greater than or equal to 1.5 times the universal gas constant (R). The present investigation was aimed to study the processing, microstructure and mechanical behavior of NiMnCrMoWx (x = 0.2, 0.4, 0.6, 0.8, 1.0 at. fraction) high entropy alloys (HEAs) fabricated through Powder Metallurgy (PM) route and Vacuum Arc Melting (VAM) process. The prescribed composition is first processed through the PM route utilizing the high-energy planetary ball mill. Milling was done for 70 h and further different characterizations like (X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Differential Scanning Calorimetry (DSC), and Transmission Electron Microscopy (TEM)) were done to find the microstructure, morphology and mechanical properties of the milled powders and sintered pellets. The results showed that the developed alloys contain both BCC and FCC phases. A decrease in the crystallite size to less than 75 nm was observed in all the compositions after 70 h of MA. The DSC results show the investigated alloys were thermally stable below 1000oC by correlating with XRD data of annealed powders at 400oC, 600oC, and 1000oC. Further, the milled powders were conventional sintered at 1200oC at Ar atmosphere for 2h holding time. Sintered pellets of all the investigated alloys were tested for density, hardness, and wear behavior. Hardness increased with increasing W content (up to 0.6 atomic fraction W) while the wear properties also were best for W0.6 alloy. Thus, a comparison of the obtained results indicated that the alloy with W0.6 atomic fraction possesses optimum combination of results. In order to have better densification, the 70 h milled powders are planned to consolidate using Spark plasma sintering (SPS). The decided alloy compositions were also processed through the VAM process at a temperature above the melting point of W the desired compositions were melted at least five times for proper mixing and homogenous particle distribution. Different physical and mechanical characterizations of the cast alloys will also be done in the next few months. Finally, a comparison of the properties of the alloys will be done as synthesized by both fabrication routes.