Variation in the martensitic transformation temperatures (TM) of quasi-ternary/off-stoichiometric Ni-Mn- Ga and Ni-Mn-Al-X alloys are correlated to their electron per atom ((e/a) ratios. The behavior of Fesubstituted Ni-Mn-Ga alloys is, however, anomalous. We use Pauling’s ideas on electronic structure of elements, and compute the number of non-bonding electrons (en) of elements, instead of the total number of electrons available beyond their rare gas shells. Using Pauling’s scheme and identifying Miedema’s electron density parameter (N) as the accurate valence of metallic elements, it has recently been demonstrated that cohesive and electronic properties of metallic systems can be assessed. From an extension of that approach, we show that TM for the quasi-ternary and offstoichiometric Ni-Mn-Ga-X and Ni-Mn-Al alloys systematically vary with the number of non-bonding electrons/atom(Nₑ⁄a). The anomalies in the case of Fe- and In-substituted Ni-Mn-Ga alloys disappear in the present case.
Author (s) Details
M. A. Mallick
Department of Physics, BMU, Asthal Bohar, Rohtak- 124021, India.
Department of Electrical Engineering, Integral University Lucknow, India.
Department of Electrical Engineering, A.M.U., Aligarh, India.
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