Detwinning deformation behaviors in Fe-Co-Ni-Al-Ti multi-component alloys

FeCoNi-based multi-component alloys have great potential for engineering applications due to their excellent mechanical properties. In this study, (FeCoNi)95(AlTi)5 and (FeCoNi)90(AlTi)10 alloys (named AT5 and AT10) were prepared by vacuum arc melting and then homogenized, cold-rolled, and recrystallized in sequence. It was found that the AT5 alloy had a single FCC phase, while the AT10 contained an FCC matrix, and L12 precipitates with a grain size of ∼4.6 nm and a volume fraction of ∼17.3%. The microstructural evolution and deformation behaviors at different deformation stages were systematically studied by in situ tensile electron backscatter diffraction. Results showed that the AT5 alloy has a yield strength of 231 MPa and a ductility of 55.4%, whereas the AT10 alloy reaches 327 MPa and 34.5%. The AT5 alloy deformed by dislocation planar slip, in contrast to the wavy slip in the AT10 alloy. The increased large-sized atoms in AT10 alloy caused significant lattice distortion and solid solution strengthening, which increased the dislocation density and enhanced strain hardening capacity. However, the solute drag and nano-precipitates led to inhomogeneous deformation within grains, promoting void formation and premature failure. Both alloys showed a strain-induced detwinning behavior at different deformation stages. Despite a lower stacking fault energy in the AT10 alloy, its annealed twin content was reduced due to the nano-precipitates and solute drag. This in situ study provides real-time and compelling insights into the deformation mechanisms of high-performance multi-component alloys.