A structural model of the orthorhombic C-3I-Al60Mn11Ni4 approximant

The interface structure of as-cast Fe--Cr--Ni/TiC(p) composite prepared by a liquid state in situ process is studied by using TEM. Ifs crack propagation feature in the process of in, situ TEM tension was also investigated. It is shown that the interface between TiC and gamma-phase is clean and tidy. No reactant is produced The orientational relationships of TiC/gamma interface are as follows: (200)gamma // (220)TiC, [001]gamma // [001]TiC (200)gamma // (200)TiC, [011]gamma // [011]TiC. Crack firstly propagates into the matrix along grain;boundary (GB) because the particulate reduces the intensify factor of stress around crack tip. Interface becomes the channel of crack propagation when crack tip is closed by the action of lattice defects. The propagation along interface causes the distortion of lattice and the piling-up of dislocation in matrix that is near the interface. Lastly, the crack changes the direction to propagate into TiC phase along subcrystalline boundary or as cleavage. The mechanism of cleavage propagation is considered that Lomer--Cottrell dislocation reaction fakes place at the connection of (010) and (101) to produce high stress concentration. This results in the initiation of microcrack and propagation of cleavage crack between (111) planes.