Features of mass transfer by N-crowdions in fcc Ni3Al lattice

Abstract

Crowdions being interstitial atoms located in closely packed atomic rows, play an important role in relaxation processes occurring in metals and alloys under severe external impacts effectively transferring mass and energy. Dynamics of crowdions motion is well studied for pure metals, while for intermetallic alloys this issue has not previously been addressed. It was earlier shown that the so-called N crowdion that involves more than one atom in its 1D motion is much more effective in frames of propagation path and excitation energy that 1-crowdion. In the present study, the motion of 1- and 2-crowdions in the Ni3Al intermetallic alloy, was studied by means of the molecular dynamics method. N-crowdion was excited by providing the same value of initial energy to N neighbouring atoms along the close-packed atomic row. It was shown that the studied crowdions can propagate along the biatomic close-packed row, but show strong instability when moving in monatomic close-packed directions. It has been established that 2-crowdions have a mean free path 2-2.5 times longer than 1-crowdions with the same initial velocity. It was also revealed that the mean free path of the nickel atom initiated crowdion than that initiated on the aluminium atom. The results suggest a higher efficiency of 2-crowdions in mass transfer in the Ni3Al intermetallic alloy. In further works, it is proposed to study the possibility of launching 2-crowdions by bombarding the crystal surface with biatomic molecules.