A First-principles Investigation On The Interfacial Bonding Properties Of Ceramic/Metal Composites

The ceramic/metal interface directly affects the mechanical and physical properties of composite materials.The bonding strength of ceramic/metal interface not only determines the effective load transfer between the metal and ceramics,but also is the bridge to establish the relationship between interface structure,interface bonding performance and macro-mechanical properties of composite materials.Also,the interfacial bonding strength is the indispensable initial parameter for the multi-scale simulation of composites,and plays the key role in functional performances of composites.However,there are still some limitations and shortcomings in the experimental study of the bonding strength of ceramic/metal interface.Moreover,the experiments take a long time and cost too much.Therefore,in this work,the first-principles calculations method has been used to establish the relationship model between the interface structures and the interfacial bonding strength of in-situ synthesized TiB/Ti and TiC/Ti,and to predict the effect of alloying elements on the interfacial bonding strength.For TiB/Ti interface,Sixteen(100)TiB/(10(?)0)α-Ti interface models considering different(100)TiB terminations and stacking sites are investigated to determine their influence on the interfacial bonding strength and thermodynamic stability by combining the existing orientation relationship of TiB/Ti interface from the in-situ experiments.The relationship between TiB/Ti interfacial microstructures and interfacial bonding strength has been revealed.Also,considering the preferred substitution position of alloying elements X(X= Al,V,Sn,Mo,Si,Zr,and Cr)in the TiB/Ti interface structure,the TiB/Ti-X interface model is established.The influence of alloying elements on TiB/Ti interface bonding strength has been revealed by using the work of separation and formation heat.The results show that for the(100)TiB/(10(?)0)α-Ti interface,the L bridge-site-B1 termination interface exhibits the strongest interfacial bonding and the most thermodynamically stable structure,forming the strong Ti-B polar covalent bonds and maintaining the same epitaxial stacking sequence as bulk TiB at the interface.After the matrix alloying,the alloying elements of V,Cr,and Mo form stronger chemical bonds with B atoms than with Ti and have the tendency to aggregate at the TiB/Ti interface region while improving its interfacial bonding strength.The alloying elements of Al,Si,Zr,and Sn generate weaker chemical bonds with B atoms and preferentially aggregate at sites away from the TiB/Ti interface.This tends to maintain or even lower the interfacial bonding strength of the interface.The calculated results,especially for V,are in good agreement with previous experimental observations.For TiC/Ti interface,six(111)TiC/(0001)α-Ti interface models are constructed based on the orientation relationship from the in-situ experiments and the types and arrangement of terminal atoms at the interface.The relationship between TiB/Ti interfacial microstructures and interfacial bonding strength has been revealed.The TiB/Ti-X interface model is established by combining the preferred substitution position of alloy elements X(X= Al,V,Sn,Mo,Si,Zr,Cr)in TiC/Ti interface structure.The effect of alloy elements on TiC/Ti interface bonding strength has been revealed by using the work of separation work and solution energy.Among these(111)TiC/(0001)α-Ti interface models,the fcc-site-C-termination interface has the greatest interfacial bonding strength and corresponds to the most stable interfacial structure,which originate from the strong Ti-C polar covalent bonds and the same epitaxial stacking sequence as bulk TiC at the interface.The calculated results of TiB/Ti-X interface indicate that the alloying elements of V,Cr,and Mo form stronger chemical bonds with B atoms than with Ti and have the tendency to aggregate at the TiB/Ti interface region.The elements of V and Cr increase the interfacial bonding strength of TiC/Ti,but Mo has little effect on the interfacial bonding strength of TiC/Ti.The alloying elements of Al,Si,and Sn are easy to diffuse near the TiC/Ti interface and react with TiC and Ti to produce the new phase Ti2MC(M= Al,Si,and Sn),which can improve the bonding strength of TiC/Ti interface.The Zr element aggregates at sites away from the TiC/Ti interface,which maintains or even decreases the bonding strength of the TiC/Ti interface.This work can provide the research method for the bonding strength of ceramic/metal interface as well as theoretical evidence to guide the design and control of the interfacial structure and bonding properties of ceramic/metal composites.