Solid Solution And Interfacial Structure Study Of Multiple Metal Elements In Ti₃AlC₂ Phase

Ti₃AlC₂,as one of the typical 312-type MAX phase ceramic phases,has excellent oxidation resistance,high specific stiffness,superior corrosion resistance,and thermal conductivity.The solid solution treatment of Ti₃AlC₂ ceramics using doping elements can improve the weaker bonding between its Al atomic layer and adjacent Ti,C atoms.Therefore,by adding different metal-active elements to undergo substitution reactions and new chemical bonds,it is not only able to enhance the strength of the MAX phase solid solution;but also to improve the wettability problems during the joining of Ti₃AlC₂ with metals.In this topic,with the help of the first-principle calculation method,replacement solid solution screening is carried out for the current potential A-position elements to replace the Al atomic layer positions in Ti₃AlC₂,mainly the following 16,including Ga,In,Si,Ge,Pb,P,As,Sb,S,Ir,Au,Fe,Co,Ni and Cu atoms.The physical and electronic properties and mechanical properties of the new solid solution Ti₃(Al_0.5A_0.5)C₂ formed by the substitution of Al atoms by these 16 A-site elements are theoretically revealed,and the metal-ceramic heterogeneous material connection or the related bonding interface structure is investigated during the solid solution process.Secondly,by designing solid-phase diffusion experiments under vacuum conditions,Ti₃Al（Ga）C₂ and Ti₃Al（In）C₂ related solid solutions were prepared by selecting Al homologous Ga and In low melting point metals and keeping Ti₃AlC₂ from decomposing;and investigating the metal-ceramic interface structure and the mechanism of solid solution and diffusion of metal atoms in MAX phase.The main findings are as follows:Using vacuum diffusion sintering experiments,Ga and In metals were insulated with Ti₃AlC₂ at 300℃for 6 h and 12 h.Subsequently,microstructure observation,physical phase analysis,energy spectrum analysis,and nanoindentation mechanical tests were performed on the sintered sample sections.the mechanism of diffusion of Ga and In metals into Ti₃AlC₂ bulk is summarized as follows,firstly,Ga and In are both active elements,and with the extension of the insulation time With the extension of holding time,micro-pores are formed on the surface of Ti₃AlC₂,and Ga and In metals flow into the micro-pores first,similar to the corrosion phenomenon.However,the paths of Ga and In elements into Ti₃AlC₂ are different;when Ga metal is sintered with Ti₃AlC₂,Ga metal flows into the Ti₃AlC₂ block along the Al atomic layer as the holding time is extended,and solid solution with Al is preferred.In metal enters Ti₃AlC₂by replacing Al atoms layer by layer and forming replacement solid solution,so the diffusion rate is slower and Ti₃Al（In）C₂ solid solution layer is formed only at the Ti₃AlC₂ boundary.