The Effects Of The Alloying Element W On The Mechanical Properties Of NiAl Intermetallic

With the increase of thrust-weight ratio of aircraft engine; turbine inlet temperature requirements are also constantly improving, high-temperature materials such as nickel-base single crystal alloy, is currently approaching its limit temperature. The physical properties of NiAl such as high strength, high melting temperature, phase stability for a wide range of chemical composition, and good corrosion resistance are of interest for applications in aerospace industry. NiAl could substitute nickel-base single crystal alloy as a new generation high temperature structural materials. However, poor ductility at low temperatures and brittle grain-boundary fracture limits its technological assignments. Therefore, improving ductility has been tried by many techniques and references therein, and among them, alloying seems to be one of the most promising approaches. The paper uses first-principles method based on density functional theory and generalized gradient approximation to study the effects of the alloying element W on the mechanical properties of NiAl intermetallic.This paper firstly establishes the calculation model and method of NiAl, then calculates the formation energy of W in Ni site and Al site respectively to determine the position of W atoms. The change of ductility of NiAl is reflected by the ratio of fracture energy and unstable stacking fault energy. And then, the effect of VIB element Cr, Mo and W on the ductility of NiAl is analyzed separately. There are many previous studies of Cr, so here is only a brief introduction; the study focuses on the effect of Mo and W on the ductility of NiAl. Finally, the electronic density maps and electronic density of states maps are analyzed to explore the reasons why the ductility of NiAl changes.Study shows that the addition of W and Mo make the unstable stacking fault energy of [001](110) slip system lower and make the fracture energy of [001](110) slip system higher,which indicates that ductility of NiAl intermetallic improves. For [100](001) slip system, the change is not obvious. The analysis of the addition of electronic density and electronic density of states shows that W and Mo strengthens the bonding between atoms in NiAl, thereby increasing the NiAl fracture energy, which makes fracture of NiAl needs more energy to occur, thus improving the ductility of NiAl intermetallic.