First Principles Study Of Ta Element On Ni₃Al Phase Transition And Phase Interface

The study of doping of rare metal elements in alloy phases has important research significance for the study of nickel-based high-temperature alloys and the development of new high-temperature alloy materials.The alloying of rare metals not only improves the strength of the alloy,but also has an important research role in the fields of oxidation resistance,corrosion resistance,and high temperature resistance.In the field of nickel-based high-temperature alloys,the alloying of W,Mo,Ta,Re and other elements is generally carried out to improve the strength of the alloy,while in the field of nickel-based high-temperature alloys research on the alloying of Ta elements,the study confirmed that Ta alloying has a beneficial effect on improving the resistance to oxidation,corrosion resistance,tissue thermal stability,creep properties and other aspects of the alloy.The volume fraction of the microstructural phase Ni3Al is the largest in nickel-based high-temperature alloys,up to70%in single-crystal nickel-based high-temperature alloys.However,few studies have been reported on the effect of Ta elemental alloying on Ni3Al phase transformation and phase interface.In this paper,the effect of Ta element doping on the phase transformation and phase interface of Ni3Al is investigated using a first-principles approach.The main elements in the study are as follows:Firstly,the effect of Ta element doping onγ’-Ni₃Al phase was investigated theoretically by first principles calculations.It was found that there exists a critical concentration of Ta element doping to makeγ’-Ni₃Al→γ’’-Ni₃Ta phase change.The critical doping concentration is 17.73（at.%）,and theγ’’-Ni3Ta phase can be generated spontaneously when the Ta element in single crystalγ’-Ni₃Al exceeds the doping concentration of 17.73（at.%）.From the thermodynamic calculations,it is also obtained that the anisotropy of the two phases exists in the relationshipγ’<γ″andγ’’-Ni3Ta has phonon dynamics stability.Secondly,it is found thatγ’-Ni₃Al andγ’’-Ni₃Ta can form a co-grid interface in the（001）low index plane by the lattice mismatch calculation.In order to further investigate forγ’-Ni3Al phase,quasi-random models with four different stacking structures were established,and it was found that the polar interface terminated by Ni atoms has the largest adhesion work and the smallest interfacial energy,which is the most stable interface.And the interface was determined to be kinetically stable by phonon calculations.Finally,an interfacial stretching simulation was performed for the model of the most stable interfacial stacking structure ofγ’-Ni₃Al andγ’’-Ni₃Ta at the（001）crystal plane.During the tensile process,it was not only found that the interfacial cracks were mainly generated inside theγ’’-Ni₃Ta crystal and at the interface bond betweenγ’-Ni₃Al andγ’’-Ni₃Ta,but also the stress-strain curve relationship diagram with strain as the variable for this interface was obtained.In the stress-strain curve relationship plot it is found that the maximum value of26.13 GPa is reached when the strain variable is at 30%.The 30%ductility indicates that the interface betweenγ’-Ni₃Al andγ’’-Ni₃Ta at the（001）crystal plane terminated by nickel atoms has good ductility,which is consistent with the Poisson’s ratio calculated by the tensile interface elastic constants,Pugh results.