Relationships Between the Sigma 9 and Sigma 27 Boundaries and the Connectivity of Random Boundary in Hastelloy C-276 Alloy

Hastelloy C-276 was subjected to 10% deformation and annealed at 1100 degrees C for different time. The fractions of Sigma 3(n)(n=1, 2, 3) boundaries and the connectivity of random boundary networks were characterized by electron back-scatter diffraction (EBSD). The results show that the Sigma 3 boundary fraction is hardly increased during the annealing period. Instead, the fractions of Sigma 9 and Sigma 27 boundaries have a dramatic change with annealing time, whose peaks are arisen after annealing for 15 min. Meanwhile, the corresponding connectivity of random boundary network is effectively disrupted. This can be attributed to the incoherent Sigma 3 boundary producing more Sigma 9 and Sigma 27 boundaries and incorporating those boundaries into the random boundary networks. Actually, the connectivity of random boundary networks can be definitely identified by Sigma(9+27)/Sigma 3 radio.