First-principles Study Of The Structure And Properties Of Al/Al₃Ti Interface

The Ti-Al₃Ti laminated composites with a shell-like structure has the characteristics of high specific strength,high fracture toughness,and low density.It is a new type of armor protection material with excellent performance.At present,the researches on Ti-Al₃Ti laminated composites have been mainly focused on the material preparation and mechanical properties test,but the study on the interfacial bond strength is not enough.In this paper,the Al/Al₃Ti interface of Ti-Al₃Ti laminated composites containing Al has been studied theoretically at the atomic scale by using first-principles method.First,the relationship between the atomic structure and properties of the Al（111）/Al₃Ti（112）interface was studied.The results showed that the interface model with center-Ⅰsite had the maximum adhesion energy（2.14 J/m²）and the strongest charge interaction,which was the best stability among the three Al（111）/Al₃Ti（112）interface models,and the interface was mainly connected by Ti-Al covalent bond.The calculated fracture work of bulk Al along the（111）direction was1.66 J/m²,which is smaller than the fracture work of interface and bulk Al₃Ti along the（112）direction.The interfacial structural cracks were more inclined to generate and diffuse in the volume phase of Al（111）plane.Then the first principles calculation method was used to simulate the tensile test of Al/Al₃Ti interface.The results showed that the maximum theoretical tensile strength of Al（111）/Al₃Ti（112）interface was 14.38 GPa.Under the action of tensile load,the Al matrix was first uniformly stretched.When the strain was greater than 25%,the sub-interface Al-Al bond and part of the interface Ti-Al bond length began to increase rapidly,local fracture occurred,and the stable structure of the tensile model was destroyed;when the strain exceeded 32.5%,more Al-Al bonds broke at the sub-interface,and the deformation failure rate of the tensile model was accelerated;tensile strain caused uneven distribution of the charge in the atomic structure,and the appearance of electron holes severely weakened the interaction between atoms.The interface structure was separated along the sub-interface,and the Al-1 atomic layer was attached to the Al₃Ti side.The tensile strength of the Al（111）/Al₃Ti（112）interface mainly depended on the strength of the Al matrix.Finally,first-principles method was used to study the effect of doping on the bonding properties of Al（111）/Al₃Ti（112）interface.The results showed that the substitutional doping of alloying elements occurred when the interface was close to the first atomic layer on the Al side,which had the greatest impact on the interface bonding performance;The adhesion work of Al（111）/Al₃Ti（112）interface doping Mn,V and Cu atom was 2.54 J/m²,2.33 J/m²,2.15 J/m²,respectively,and formed Mn-Ti,V-Ti and Cu-Al chemical bond at interface,which improved the interface bonding strength;the doping of Zn,Si,Mg and B elements will weaken the interaction between the interface atoms,which was not conducive to the interface bonding;The increased amount of doping Mn and V elements can increase the adhesion work of the interface model,enhance the charge density between atoms at the interface,and improve the interface bonding strength.