The effect of elastic anisotropy on dislocations in Ni₃Fe

Abstract

The single crystal elastic constants of Ni₃Fe were measured by an ultrasonic interferometric technique in the temperature range -196° to 300°C. Both C₁₁ and C₄₄ decrease with increasing temperature, while C₁₂ remains almost constant below room temperature, then increases with temperature up to 100°C and subsequently decreases as temperature increases further. The constants have been used to calculate 1) the interaction force between parallel Shockley partial dislocations and 2) the energy factor of a straight perfect dislocation as a function of dislocation orientation. While dissociation of a screw dislocation seems quite normal, the forces between partials in a dissociated edge dislocation are attractive at -196° and 100°C. In general, the maximum stacking fault energy for which dissociation is energetically favorable, γ_m, decreases as temperature increases. Inverse Wulff plots indicate that thea/2 <110> total dislocation in Ni₃Fe is stable for all orientations and temperatures.