Influence of Fe substitutions on the deformation behavior and fault energies of Ni 3Ge–Fe 3Ge L1 2 intermetallic alloys

Abstract

Ni 3Ge exhibits a yield strength anomaly, whereas the yield strength of Fe 3Ge shows a normal decline with temperature, and there is a gradual transition from anomalous to normal behavior as Fe content increases. A dramatic strengthening for 77 K deformation has also been noted to occur in these alloys as a result of increasing Fe content. The combined use of transmission electron microscopy (TEM) and image simulations has facilitated identification of the operative deformation mechanisms and allowed for a quantitative measure of superdislocation dissociations. A transition from octahedral glide and Kear–Wilsdorf locking to cube glide of superdislocations has been observed to coincide with an increase in either deformation temperature or Fe content. The low-temperature strengthening has been correlated with enhanced cross-slip, which is aided by a significant lowering of the cube-plane antiphase boundary energy with increasing Fe content. It is proposed that the strengthening and the transition to cube glide are promoted by an increase in the complex stacking fault energy, which enhances both cross-slip and cube-plane mobility.