Ductility enhancement by boron addition in Co-Al-W high-temperature alloys

The mechanical properties of several B-free and B-doped Co-Al-W superalloys with different volume fractions of the Co3(Al,W)-γ' phase were examined by mechanical tests at various temperatures up to 980 oC. Although grain boundary fracture occurred in the B-free alloys, the addition of a small amount of B drastically improved the ductility. It was also confirmed that the positive temperature dependence of strength was strongly affected not only by the volume fraction of the γ' phase, but also by the addition of B.