Correlating work hardening with co-activation of stacking fault strengthening and transformation in a high entropy alloy using in-situ neutron diffraction

Abstract

Transformation induced plasticity (TRIP) leads to enhancements in ductility in low stacking fault energy (SFE) alloys, however to achieve an unconventional increase in strength simultaneously, there must be barriers to dislocation motion. While stacking faults (SFs) contribute to strengthening by impeding dislocation motion, the contribution of SF strengthening to work hardening during deformation is not well understood; as compared to dislocation slip, twinning induced plasticity (TWIP) and TRIP. Thus, we used in-situ neutron diffraction to correlate SF strengthening to work hardening behavior in a low SFE Fe40Mn20Cr15Co20Si5 (at%) high entropy alloy, SFE ~ 6.31 mJ m−2. Cooperative activation of multiple mechanisms was indicated by increases in SF strengthening and γ-f.c.c. → ε-h.c.p. transformation leading to a simultaneous increase in strength and ductility. The present study demonstrates the application of in-situ, neutron or X-ray, diffraction techniques to correlating SF strengthening to work hardening.

Tuning Microstructure and Mechanical Performance of a Co-Rich Transformation-Induced Plasticity High Entropy Alloy

“…In addition, the improvement in the σ y in the WR sample was attributed to ∆σ g , ∆σ d , and ∆σ SF . It was proposed that SFs act as impediments for dislocation slip, similar to other immobile boundaries [38,39]. The ∆σ SF is linearly proportional to the SF density.…”

Role of planar faults in martensite formation in nano-polycrystalline iron by molecular dynamics simulation

“…Hence, it is reasonable to assume that the increase of twin density will decrease the M s due to a reduction in the grain size, but a clear effect of the presence of twins in the austenite phase on the martensitic transformation is not yet known. The dislocation motion can be blocked by the SFs and nano twins, which would contribute to austenite strengthening [36,37]. It follows that the presence of these defects should hinder the austenite to martensite transformation.…”