Multiscale Architecture Strengthening-Toughening Design And Mechanical Properties Of Bioinspired TiAl-based Alloys

With the development of high-tech fields such as aerospace,the properties requirements for materials are also increasing.In recent years,TiAl-based laminated composite sheets have received extensive attentions as a new type of lightweight structural materials.However,the poor ductility at room temperature and insufficient high temperature strength of TiAl-based laminated composite sheets have caused the limitations of load-bearing capacity,which restricted their practical application.Based on the concept of multi-scale composite configuration,Ti-Al-TiC mixed powder and through-hole titanium alloy foil(Ti-6Al-4V)were alternately stacked to prepare TiAl based laminated composite sheets by spark plasma sintering.The phase composition,interface structure and composition,laminated structure,crack propagation characteristics,room temperature mechanical properties,and the strengthening and toughening mechanism of the samples were studied.The results indicated that the composite layer of the samples was mainly composed of?₂-Ti₃Al/?-TiAl dual phases,and carbide phases(Ti₂AlC,TiC).The laminated structure characteristics were very obvious.The Ti₃Al interface phases were generated between the composite layer and the toughening layer,and the interface was well bonded.The Ti₂AlC reinforcements in the composite layer were distributed at the matrix grain boundaries with a network feature.The performance of the TiAl-based laminated composite sheet corresponding to A-type holes with seven TC4 layers and 0 wt%theoretically generated content of Ti₂AlC was the best.The room temperature flexural strength and fracture toughness of the product parallel to the lamination direction were 1165.35 MPa and 34.90 MPa·m^1/2,respectively.The room temperature flexural strength and fracture toughness of the product perpendicular to the lamination direction were 722.68 MPa and 28.55 MPa·m^1/2,respectively.The performance of the TiAl-based laminated composite sheet corresponding to B-type holes with seven TC4 layers and 5 wt%theoretically generated content of Ti₂AlC was the best.The room temperature flexural strength and fracture toughness of the product parallel to the lamination direction were 1068.65 MPa and 35.57 MPa·m^1/2,respectively.The bending strength and fracture toughness of the product perpendicular to the lamination direction were690.47 MPa and 29.49 MPa·m^1/2,respectively.The performance of the TiAl-based laminated composite sheet corresponding to AB-type holes with seven TC4 layers and 10 wt%theoretically generated content of Ti₂AlC was the best.The room temperature flexural strength and fracture toughness of the product parallel to the lamination direction were 872.88 MPa and 27.69 MPa·m^1/2,respectively.The bending strength and fracture toughness of the product perpendicular to the lamination direction were 759.43MPa and 27.31 MPa·m^1/2,respectively.TiAl-based laminated composite sheet achieved nearly isotropy.Ti₂AlC reinforcement can not only effectively inhibited the growth of?-TiAl/?₂-Ti₃Al,refine the grain size,but also weaken the driving force of crack propagation and increased the resistance of crack propagation.The through-hole laminated configuration realized the effective connection between layers,and the laminated structure had geometric constraints and energy dissipation,which greatly improved the performance of composite sheets.In short,the through-hole laminated composite structure design effectively realized the strengthening and toughening effect.