Empirical mapping of ZrCu-based alloys with valence electrons versus transformation temperatures

Abstract

An empirical map of martensitic transformation temperatures versus average valence electrons per atom (e v/a) and valence electron concentration (c v) was developed in order to design ZrCu-based shape memory alloys (SMAs). The martensitic transformation temperatures of about 40 different alloys (Ni, Co, Hf, Ag, Ti, Al, Cr, etc.), covering nearly all possible replacements of Zr or Cu, are exhibited. The relationship between transformation temperature and cv or electron density (n) was determined. The results indicate that the transformation temperatures of ZrCu-based alloys gradually decrease until reaching an inflection point at c v = 0.218, above which the transformation temperatures go down. A linear dependence of the transformation temperatures of ZrCu-based alloys on the electron density is revealed by data-fitting. Under the guidance of these contour maps describing transformation temperatures and thermal hysteresis, a series of ZrCu-based alloys that can function under different conditions can be designed.