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Microstructure observation suggested that slowing down the cooling rate influence γ′ precipitation obviously and consequently produces coarse γ′ which could significantly improve plastic flow behavior that helps to break down the cast microstructures of wrought superalloys with high volume fraction of γ′. After full recrystallization, a modified dual-phase microstructure containing refined γ matrix plus coarse γ′ shows superplasticity during subsequent hot deformation. It also proved that soft lagging casing method is effective to retard the surface heat radiation of the pre-heated ingots during cogging operation.