分步退火及初始晶粒对Hastelloy C-276合金晶界特征分布影响

不同初始晶粒尺寸的 Hastelloy C-276 合金经冷轧变形后，分别采用一次退火和二次退火方法进行热处理，其晶界特征分布采用电子背散射衍射技术进行表征.结果表明，初始较大晶粒组织有利于晶界特征分布的优化，特殊晶界比例比小尺寸晶粒组织提高了近10%，达到了78.8%，同时形成了平均尺寸为200μm晶粒团簇组织.在相同晶粒尺寸条件下，采用二次退火工艺可以明显改善合金的晶界特征分布，∑3^○n晶界比例得到较大幅度的提高，并形成了良好的团簇组织.这是由于较多的非共格∑3晶界，容易产生∑9和∑27晶界，从而形成更多的三叉晶界，阻断了大角度晶界的连通性.

Effects of Two-Step Annealing and Initial Grain Size on the Grain Boundary Character Distributions of Hastelloy C-276

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.