On prominent TRIP effect and non-basal slip in a TWIP high entropy alloy during high-pressure torsion processing

Severe plastic deformation response of a face centered cubic (FCC) twinning induced plasticity (TWIP) high entropy alloy (HEA), Fe40Mn40Co10Cr10, subjected to high-pressure torsion (HPT) is investigated. The so-called TWIP HEA demonstrated an extensive transformation induced plasticity (TRIP) effect even in ½ turn (shear strain, γ = 15) of HPT processing, which increased further with increasing the number of turns to 2 (γ = 68). Additionally, HPT induced nano-structuring and heavily dislocated structure; dislocation density was of the order of 1015 m−2. c/a ratio of the transformed HCP phase was found to be <1.633 and it did not change with increasing the extent of shear strain. This was manifested as the occurrence of at least 50% non-basal slip in the HCP phase. For the first time, the fraction of and dislocations are quantified and their evolution are discussed in the purview of the studied alloy. The micro-mechanism of strain accommodation is correlated with increasing hardness of the HEA upon sequential HPT processing. The present work provides a viewpoint that the deformation induced HCP phase in a metastable FCC HEA can have tailored c/a ratio which triggers non-basal slip, leading to a strong and ductile material.