Study On Deformation And Fracture Behavior Of Ti/TiAl₃/Al Layered Composites

Heterogeneous layered configuration design can well combine the excellent properties of each component metal and achieve the synergistic improvement of strength and plasticity that is difficult to achieve in traditional alloys.Intermetallic have been difficult to use because of their brittleness at room temperature.Through the idea of heterogeneous layered configuration design,researchers combined the ductile metal layer with the brittle intermetallic layer to create the metal/intermetallic compound layered composite.However,due to ignoring the factors of intermetallic scale,the elongation of these metal/intermetallic layered composites is very poor.In this paper,three kinds of Ti/TiAl₃/Al laminated composite plates with TiAl₃layers with different thickness were prepared by adjusting vacuum hot pressing sintering parameters with pure Al foil and pure Ti foil as raw materials.Through the tensile property test at room temperature,it is found that the thickness of TiAl₃ layer is 1?m,the material can show excellent comprehensive mechanical properties.Comparing the results of tensile properties and rule of mix,it is found that Ti/TiAl₃/Al laminated composite plate achieves very high yield strength,which is far beyond the predicted value of rule of mixtures.At the same time,it can also have excellent plasticity.Aiming at the scientific problem of strengthening and toughening of Ti/TiAl₃/Al layered composites,the relationship between"Local strain evolution-Deformation texture evolution-Crack distribution evolution"of Ti/TiAl₃/Al layered composites is established based on digital image correlation,in-situ electron back scattering diffraction and three-dimensional X-ray tomography.By analyzing the stress state in the deformation process,it is judged that the deformation process is mainly divided into five stages:elastic-elastic-elastic stage,elastic-elastic-plastic stage,elastic-plastic-plastic stage,initial stage of plastic deformation and later stage of plastic deformation.Through the distribution and evolution of local strain,it is found that the layered structure well transmits the concentrated strain in TiAl₃ layer.At the same time,TiAl₃ layer can well restrict the deformation of Ti layer and Al layer in the early stage of deformation.Through the evolution of microstructure during material deformation,it is found that the start ofslip is found in the region of Ti layer close to TiAl₃ layer in the early stage of deformation.Starting the pyramidalslip requires a greater critical shear stress,which makes the Ti layer yield at a higher stress level,resulting in a prediction beyond the rule of mix.At the same time,according to the results of geometrically necessary dislocation,it is found that strain localization occurs in Ti layer with the increase of deformation.The strain localization near the interface is the highest.This is mainly result the formation of back stress and dislocation strengthening caused by dislocation accumulation near the interface.Through the analysis of crack distribution and evolution,it is found that when the number and distribution of cracks in the intermetallic compound layer reach the critical limit,the ductile failure of Ti layer leads to the fracture of the material.The thickness of TiAl₃ layer determines the crack size in TiAl₃ layer and the elongation of the material.The size and number of through cracks can be controlled by reasonably adjusting the thickness of TiAl₃ layer.The smaller the size and the more uniform the number of through cracks,the more conducive it is for the Ti layer to release the stress at the crack tip through uniform plastic deformation,passivate the cracks,and make the material obtain excellent plasticity.