Title: Effect of Ag and Si on the microstructures in Al-Cu-Ni-Mn-Ag/Si ternary high entropy alloy

Abstract

The microstructures developed by the addition of (a) Ag and (b) Si in Al-Cu-Ni-Mn HEA alloy have been compared. The alloys were prepared by melting pure metals of at least 3 nines purity in electric arc furnace followed by casting. The alloys were repeatedly melted and cast several times to ensure a homogeneous distribution of the metals in the castings. The as cast microstructures in the monolithic form and as modified by Si and Ag were examined by the SEM in the back scattered electron mode. EDS was used to identify the compositions of the phases and x-ray color mapping was used to determine the locations of different elements in the microstructures. Phases developed, as identified by the compositions in atomic percent, were compared to ascertain the role of additives in the monolithic form. Monolith microstructure consists of three phases rich in (a) Al-Cu-Ni with gray contrast, (b) Ni with white contrast, and (c) Mn with black contrasts. Ag and Si alloys show similar three phases but variations in contrast. Phases in Ag alloy are rich in (a) Al-Cu-Mn, gray, (b) Ni, black, and (c) Ag, white, while the phases present in Si alloy are rich in the following elements: (a) Al Cu-Mn, gray, (b) Ni, white, and (c) Mn, black contrasts. The compositions of the phases in the alloys may also be related to the atomic radii of the elements in the phases. The ratio of the two richest elements in the phases show that if their atomic radii are within ±15% of each other then they attract other elements also in that phase. On the other hand, for ratios of the atomic radii for the two richest elements that are not within ±15%, other elements are not attracted towards this phase.

Biography

S.K. Varma is a professor in the department of Metallurgical, Materials, and Biomedical Engineering at the University of Texas at El Paso since 1984. He teaches Nanofunctional Physical Metallurgy, Mechanical Behavior of Materials at this time. He has taught many courses both at graduate and undergraduate levels. He is the recipient of many awards including Best Teaching and Distinguished Achievement in Research. He has been conducting research in many physical and mechanical metallurgy areas: large strain plastic deformations, static annealing, composite materials, corrosive wear, refractory metals, and high entropy alloys. The research has yielded nearly 100 peer reviewed journal publications, numerous proceedings papers and supervision of 35 graduate students for their master’s theses and Ph.D. dissertations. Organizers of the conferences, chairing many sessions in MS&T and TMS conferences, reviewing manuscripts for many peer reviewed journals are few of the other professional activities with which he is involved with.