Kinking nonlinear elastic deformation of Ti3AlC2, Ti2AlC, Ti3Al(C0.5,N0.5)2 and Ti2Al(C0.5,N0.5)

In this paper four ternary MAX phases, Ti3AlC2, Ti2AlC, Ti3Al(C0.5,N0.5)2 and Ti2Al(C0.5,N0.5), were fabricated by hot pressing or hot isostatic pressing. The microstructures were characterized and found to be comprised of plate-like grains, 70–130 μm in diameter and 5–10 μm thick. Because all compositions traced fully reversible, reproducible, hysteretic loops during uniaxial cyclic compression tests they were classified as kinking nonlinear elastic (KNE) solids. When the results were analyzed using our recently developed microscale incipient kink band (IKB) model, the various relationships predicted among the three independently measured values – stress, nonlinear strain and dissipated energy – were exceptionally well adhered to. From the results we estimate the critical resolved shear stresses, CRSS, of the basal plane dislocations to range from 24 to 60 MPa. We also show that the relationship between the CRSS and grain size is of a Hall-Petch type. The reversible dislocation density is estimated to be (1–9) × 1013 m−2 at stresses that ranged from ≈300 to 650 MPa.