Solid-solution Strengthening of FCC Complex, Concentrated Alloys

Chia-Hsiu Chang, Purdue University

Abstract

Concentrated complex alloys (CCAs) have a twelve-year history, are composed of various alloying elements, and typically belong to random solid-solution alloys. Due to the complex nature of the alloy compositions, a vast range of alloy compositions are possible, and some alloys have been observed to exhibit complex deformation mechanisms. However, the mechanisms of strengthening in CCAs are not clear at present. Traditional models fail to provide the insight necessary to predict solid-solution strengthening in CCAs. Recently, an elasticity-based model was developed for predicting the strength of CCAs, but its applicability has been constrained to those alloys comprised of only face-centered cubic (FCC)-stable elements. Our study hypothesizes CCAs as a pseudo-binary alloys, whose solutes include elements with different stable room temperature crystal structures besides FCC, with an aim to validate and extend the aforementioned model’s applicability. To validate the new model, we performed x-ray diffraction, differential thermal analysis, and tensile property measurements to determine atomic misfit volume, transformation temperatures, and yield strengths of various CoFeMnNi-based alloys with different alloying additions (Al, Cu, Cr, Mo, Ti, and V). The experimental results will be compared to the strengthening model, and implications for alloy design will be discussed.

Degree

M.S.M.S.E.

Advisors

Titus, Purdue University.

Subject Area

Materials science

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