Slip, twinning, and fracture at a grain boundary in the L12 ordered structure—AΣ = 9 tilt boundary

M. H. Yoo, A. H. King
1988 Journal of Materials Research  
The role of interaction between slip dislocations and a 1 = 9 tilt boundary in localized microplastic deformation, cleavage, or intergranular fracture in the L12 ordered structure has been analyzed by using the anisotropic elasticity theory of dislocations and fracture. Screw superpartials cross slip easily at the boundary onto the ( i l l ) and the (001) planes at low and high temperatures, respectively. Transmission of primary slip dislocations onto the conjugate slip system occurs with a
more » ... ain degree of difficulty, which is eased by localized disordering. When the transmission is impeded, cleavage fracture on the (111) plane is predicted to occur, not intergranular fracture, unless a symmetric double pileup occurs simultaneously. Absorption (or emission) of superpartials occurs only when the boundary region is disordered. Slip initiation from pre-existing sources near the boundary can occur under the local stress concentration. Implications of the present result on the inherent brittleness of grain boundaries in Ni3 Al and its improvement by boron segregation are discussed. 848
doi:10.1557/jmr.1988.0848 fatcat:3wssxg3vujbhxmrxqae57w4feu