Discontinuous elastic strain observed during stretching of NiAl single crystal nanofilms

Uniaxial tension of a NiAl nanofilms with prismatic dislocation loops is simulated via molecular dynamics. The NiAl intermetallic compound with B2 superstructure has very few slip systems, which results in elastic deformation of the nanofilm up to fracture at tensile strain as large as 0.308, despite the presence of dislocations. Fracture takes place at the tensile stress of 14.9 GPa, which is close to the theoretical limit. The stress-strain curve of the elastic deformation has a range where the deformation develops at decreasing tensile stress. Within this range the domains with two different values of elastic strain coexist in the nanofilm. A quasi-discontinuous jump of the elastic strain occurs at the domain walls. Elastic strain at decreasing stress takes place due to increase of the domains with larger strain at expense of the domains with smaller strain.