Tensorial interaction model for the effect of short-range order on single crystalline medium entropy alloys

•Mechanism based crystal plasticity theory is proposed for single crystalline CrCoNi.•A tensorial model is for the first time developed for the SRO-dislocation interaction.•Decrease of the flow stress is induced by the destruction of short-range orders.•Theoretical results match well with experimental data of single crystalline CrCoNi. In order to help comprehend the influence of short-range order (SRO) structures on both the mechanical property and microstructural evolution of single crystalline medium entropy alloys (MEAs), a physical mechanism-based crystal plasticity theory is developed in this work, which covers the deformation mechanisms of dislocation-SRO interaction, network dislocation interaction, dislocation-twin boundary interaction, twinning deformation and solid solute strengthening. Thereinto, a tensorial interaction model is proposed to effectively characterize the spatial interaction between SROs on the characteristic planes and dislocations on the slip planes, which can not only address the increase of yield stress related to the impediment of slip dislocations by SROs, but also capture the phenomenon of decreasing flow stress after the yield point due to the destruction of SRO structures. Moreover, twinning deformation has been additionally taken into account by considering the complex hardening behavior related to both co-planar and non-co-planar twinning. To help validate the proposed constitutive equations, the stress-strain relations of single crystalline CrCoNi under three different loading directions are compared between the experimental data and theoretical results. A good agreement is achieved that can help verify the proposed theoretical model and facilitate the comprehension of the underlying deformation mechanisms.