Abstract: Hastelloy C-276 samples with different initial grain sizes were subjected to one-step and two-step annealing heat treatments after cold-rolling process and their grain boundary character distributions (GBCDs) were characterized by electron backscatter diffraction (EBSD) techniques. The results show that the large-sized initial grains tend to optimize the GBCD. Compared with that in the small-sized grain ones， the fraction of coincident site lattice (CSL) boundary in Hastelloy C-276 samples with large-sized initial grains increases nearly 10%， which is up to 78.8%. Meanwhile， the clusters with average size of 200μm are formed. For the samples with same-sized grains， the GBCD can be well improved by the two-step annealing treatment， where the fraction of ∑3^○n boundaries can be increased significantly and the better clusters can be formed. The more incoherent ∑3 boundaries， the more ∑9 and ∑27 boundaries can be generated， leading to the more triple junctions. Therefore， the connectivity of the high-angle grain boundary network is disrupted effectively.

Key words: two-step annealing heat-treatment, initial grain size, Hastelloy C-276 alloy, special grain boundary, grain boundary character distribution(GBCD)