Microstructural and Mechanical Properties of TiC_X–Ni₃(Al,Ti)/Ni Functionally Graded Composites Fabricated from Ti₃AlC₂ and Ni Powders

In this paper, a novel type of functionally graded material (FGM) was successfully fabricated from pure Ni and Ti₃AlC₂ powder mixtures by hot-press sintering route at 1200 °C and 17 MPa. In each layer, Ti₃AlC₂ particles transformed into TiC_x phase, while the additional Al–Ti atoms decomposed from Ti₃AlC₂ diffused into the Ni matrix, giving rise to the formation of γ′-Ni₃(Al,Ti). Part of the submicron TiC_x and Ni₃(Al,Ti) particles were uniformly distributed in the Ni matrix, while some of the TiC_x maintained the original Ti₃AlC₂ plate-like morphology. Both TiC_x and Ni₃(Al,Ti) content decreased from 60Ti₃AlC₂/Ni layer to 10Ti₃AlC₂/Ni layer in a stepwise manner was fabricated. The microstructural analysis indicates that no cracks, delamination and step-type abrupt changes occured in the graded layer of the manufactured FGM. Flexural strength and Vickers hardness enhanced with the increasing Ti₃AlC₂ content except for fracture strain and toughness. The overall fracture toughness and the flexural strength of FGM can reach 21.76 MPa m^1/2 and 1329 ± 34 MPa, respectively. The prepared FGM, herein, with a hard ceramic surface on one side to resist local plastic deformation, and a ductile metallic surface on the other side to provide toughness.