Superplastic Ni-Co base alloy and superplastic working method thereof

摘要

PURPOSE: To facilitate the working of an Ni-Co-base alloy into a shape requiring large deformation or a complicated shape at low stress and also to make it possible to perform forming, conventionally performed by multistages, by a single stage. CONSTITUTION: An Ni-Co-base alloy, having an alloy composition consisting of, by weight ratio, 31.4-33.4% Ni, 19.5-20.5% Cr, 9.5-10.5% Mo, 0.8-1.2% Nb, 0.3-0.7% Ti, 1.1-2.1% Fe, and the balance Co, is used. This alloy is subjected to solution heat treatment and then cold-worked at =30% draft, by which fine deformed twins are formed in a base phase. Then, plastic working is done at =10-3 /S strain rate at a temp. in the region between 750 and 900 deg.C and not lower than the recrystallization temp.