Interface Doping Effects And Mechanical Properties Of SiC/Ti And TiB/Ti Composites

Compared with titanium alloys,titanium matrix composites(TMCs)have high strength and good high-temperature mechanical properties.However,TMCs also have problems such as interface reaction and interface debonding having adverse effects on its mechanical properties.Moreover,the relationship among interface microstructure,interface binding and mechanical properties is still unclear due to the complex interface structure in the experimentally fabricated composites.Considering that reinforcing phases SiC and TiB are most widely used in TMCs,in this paper,the first-principles calculations are used to study the interface binding,theoretical strength and elastic properties of SiC/Ti and TiB/Ti systems with matrix and reinforcing phase doped,respectively.Combined with the analysis of electronic structure,the relationship among interface microstructure,interface binding and mechanical properties is revealed.For SiC/Ti system with matrix doped,it is found that Mg and Al dopants increase the interface binding of the SiC/Ti system.Si dopant hardly changes the interface binding,while Sc,Y,Ni,Cu and Mn dopants reduce the interface binding.However,only Y,Al and Si dopants enhance the elastic modulus,and Sc,Mg,Ni,Cu and Mn reduce the elastic modulus.This suggests that the elastic modulus of the SiC/Ti system is not directly dependent on the interface binding.The analysis of electronic structure reveals that the elastic modulus is also related to the localization of electron distribution.With the uneven degree of the electron distribution at the interface increases,the ionic bond or covalent bond content at the interface is enhanced and the elastic modulus increases.In addition,the Mn-doped SiC/Ti interface reduces the elastic modulus due to the large lattice distortion.For TiB/Ti system with reinforcing phase doped,it is found that V and Mo provide excess electrons to increase the electrons accumulating at the interface and thus,the interface binding is enhanced.Zn provides vacancy to decrease the interface electron,while Y and Al dopants cause lattice distortion,both resulting in the interface binding weakened.The calculation on mechanical properties shows that V and Mo dopants improve the theoretical strength of the interface system,while Zn,Al,V and Mo dopants reduce the elastic modulus of the interface system.It indicates that the theoretical strength is positively correlating with the interface binding,while the elastic modulus is not directly dependent on the interface binding.In addition,V and Mo dopants increase the elastic modulus of TiB which might hinder the crack propagation.The above research results provide theoretical support for the design and application of high strength TMCs.