Microstructure evolution and brazing mechanism of Ti2AlC–Ti2AlC joint by using pure-silver filler metal

Abstract

This paper investigated the microstructure evolution of a Ti2AlC–Ti2AlC joint brazed using pure-silver filler metal at 1030°C for 5min, characterized the newly formed products in the joint and elucidated their formation mechanism. Furthermore, it reveals the effect of Ag on the crystal structure of Ti2AlC. Ti2AlC is perfectly bonded by using Ag filler, with no crack or pore being observed. During brazing, the molten Ag filler metal infiltrates into the Ti2AlC along the grain boundaries. Al and Ti migrate out of Ti2AlC and dissolve into the Ag, forming the Ag[Al, Ti] solid solution. Ag3[Ti, Al] is produced on the basis of Ag[Al, Ti] through ordering transition during the cooling process. Simultaneously, Ag element diffuses into the crystal structure of Ti2AlC. Nevertheless, the Ti2AlC retains its crystal structure under the partial loss of Al and Ti. The shear strength of the joint was 132±8MPa, nearly 73% of that of the Ti2AlC substrate.