Probing deformation behavior of a refractory high-entropy alloy using in situ neutron diffraction

The grain orientation-dependent lattice strain evolution of a (TiZrHfNb)98N2 refractory high-entropy alloy (HEA) during tensile loading has been investigated using in situ neutron diffraction. The equivalent strain-hardening rate of each of the primary -oriented grain families was found to be relatively low, manifesting the macroscopically weak work-hardening ability of such a body-centered cubic (BCC)-structured HEA. This finding, along with the post-mortem transmission electron microscopy (TEM) characterization, is indicative of a dislocation planar slip mode that is confined in a few single-slip planes and leads to in-plane softening by high pile-up stresses. In particular, during plastic deformation, the <110>-oriented grains yield preferentially, followed by lattice relaxation, while the load transfers to the <200>-oriented grains as a result of plastic anisotropy. Our work provides a new perspective for understanding the strain-hardening behavior and the role of planar slip in the plastic deformation of BCC-structured HEAs.

Automated summary

The grain orientation-dependent lattice strain evolution in a (TiZrHfNb)98N2 alloy during tensile loading was investigated using in situ neutron diffraction. The alloy exhibited a relatively low strain-hardening rate, indicating weak work-hardening ability. Transmission electron microscopy revealed a dislocation planar slip mode confined to a few single-slip planes, leading to in-plane softening due to high pile-up stresses. During plastic deformation, <110>-oriented grains yielded first, followed by lattice relaxation, and then the load transferred to <200>-oriented grains due to plastic anisotropy.