Effect of boron on grain boundary character distribution in Ni3Al

摘要

Polycrystalline NijAl exhibits severe grain boundary brittleness In an ambient environment. In the past two decades, considerable efforts have been devoted to finding the cause of the brittleness and to improving ductility [1-4], It has been found that, in-NijAl; the grain boundary brittleness strongly depends on the grain boundary characters and their distribution (GBCD) [5,6]. The low angle boundaries (LAB) and ?3 twin boundaries exhibited much higher fracture resistance than other boundaries [5,6]. The ductility of NbA! can be increased by increasing the fraction of LAB and E3 boundaries. For example, a 45% elongation in dry air could be achieved by increasing LAB and 13 to 29.2% [7], In moist air, it was estimated [8] that a higher fraction of LAB and S3 boundaries (> 60%) would be required for the alloy to resist moisture-induced embrittlement.