Effect of Interphase Boundary Character on Mechanical Properties in NiAl(beta) Bicrystals with Ni_3Al(gamma') Precipitates along Grain Boundary

摘要

Role of the crystallography of Ni_3Al(gamma')precipitates along grain boundaries of NiAl(beta) in mechanical properties was systematically investigated using beta bicrystals with controlled orientations. gamma' phase preferentially precipitated along beta grain boundaries showing a film- like shape. The selected variant of gamma'-film satisfied the Kurdjumov-Sachs (K-S) relation with a neighboring A crystal but it deviated from the relation with another adjacent A crystal. In the course of tensile deformation at room temperature, fracture occurred preferentially at incoherent (beta/gamma') interphase boundary deviating from the K-S relation and the fracture stress decreased with increasing deviation angle. In contrast, the interphase boundary sliding occurred preferentially at irrational (beta/gamma') interface at 1073K. The sliding displacement increased with creasing deviation angle. Thus, the mechanical properties of beta bicrystals with gamma'-film were found to depend strongly on the interphase boundary character.