Assessing the Correlation of Martensitic Transformation Temperatures of Ni-Mn-Ga/Al-X Alloys to Non-Bonding Electron Concentration

Variation in the martensitic transformation temperatures of quasi-ternary/off-stoichiometric Ni-Mn-
Ga and Ni-Mn-Al-X alloys are correlated to their electron per atom 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 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 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. The anomalies in the case of Fe- and In-substituted Ni-Mn-Ga alloys disappear
in the present case.