Precipitate varies at the grain
boundaries of Ni-30Cr-1Cu alloy.It
precipitates little at the primary carbides but much easier at the second carbides.Different grain size with similar amount of precipitates at grain boundaries was obtained after the alloys were in solution at different temperatures and cooled quickly in salt water.Results show that the impact
toughness and tensile
ductility at room temperature are
increased variably together with the increase of the grain size.After being solved at 1180℃ and cooled at different rates,the amount and distribution density of M 23 C 6 at grain boundaries increased remarkably when the cool rate went down.Morphology of precipitates transformed from fine lamellae in air cool
condition to particles,rods and films,even to dendrite in slow cool condition.Due to this conformation,grain boundaries became
fragile,and the impact toughness and the tensile ductility decreased obviously.Fracture morphology transformed from mixed ones dominated by trans-grain to intergrain fragile ones.