First-Principles Investigation on Phase Stability, Elastic and Magnetic Properties of Boron Doping in Ni-Mn-Ti Alloy

The all-d-metal Ni-Mn-Ti Heusler alloy has giant elastocaloric effect and excellent mechanical properties, which is different from the conventional Ni-Mn-based Heusler alloys. In this work, the preferred site occupation, phase stability, martensitic transformation, magnetic properties, and electronic structure of the B-doped Ni2Mn1.5Ti0.5 alloys are systematically investigated by the first-principles calculations. The results show that B atoms preferentially occupy the octahedral interstitial. The doped B atoms tend to exist in the (Ni2Mn1.5Ti0.5)1-xBx (x = 0.03, 0.06, 0.09) alloy in the form of aggregation distribution, and the martensitic transformation temperature decreases with the increase in the B content. For octahedral interstitial doping, the toughness and plasticity of the (Ni2Mn1.5Ti0.5)1-xBx alloys decrease, but the strength and rigidity are greatly enhanced. This is because a small part of the d-d hybridization in ternary Ni-Mn-Ti alloy is replaced by the p-d hybridization in Ni-Mn-Ti-B alloy.