Cryogenic micropillar compression of Ti3AlC2, Ti3SiC2 and Cr2AlC: A comparative evaluation of composition-dependent dislocation mobility in MAX Phases

MAX phases serve as an ideal model system for studying the crossover between metallic and ceramic behavior, and improved ceramic ductility. This ductility is primarily linked to the anomalously easy glide of basal plane dislocations, yet a full theoretical understanding of the characteristics governing their mobility remains a subject of continuing research. Following recent efforts using atomistic simulations of MAX phase basal plane dislocation cores, the present study focused on an experimental evaluation of friction and Peierls stresses in three representative MAX phase compounds, Ti3AlC2, Ti3SiC2, and Cr2AlC, using micropillar compression at cryogenic temperatures. The study examines specifically the effects of temperature, size, and pristine dislocation morphology under aid of crystal plasticity finite element simulations to derive the lattice resistance for each compound and compare it with previously simulated results. Measured Peierls stresses of 142 MPa (Ti3AlC2), 150 MPa (Ti3SiC2), and 359 MPa (Cr2AlC) confirm a significant role of core structures and bonding characteristics on MAX phase dislocation plasticity, with Ti-based MAX phases exhibiting markedly lower lattice resistance than Cr-based compounds. The cryogenic tests presented here mark the first such experiments in MAX phases and open new pathways for understanding their deformation behavior at low temperatures.