Strengthening behavior of Al and Ti elements at room temperature and high temperature in modified Nimonic 80A

Nickel-based superalloy Nimonic 80A modified with various Al and Ti contents has been developed. The γ′ coherently precipitates in the γ matrix on {100}γ′/γ and {110}γ′/γ atomic planes. The volume fraction of γ′ increases significantly with the increase of Al and Ti contents. But the volume fraction of γ′ decreases after stress-rupture tests compared with that after full heat treatment, which is primarily due to the coarsening of γ′ and the increased width of γ matrix channel. The strengthening effect of Ti is more significant than that of Al at room temperature. While the strengthening effect of Al is more significant than that of Ti at 750°C/310MPa. The increased volume fraction of γ′ leads to the increased room temperature tensile strength and stress-rupture life at 750°C/310MPa. However, the η-Ni3Ti is identified after full heat treatment in the alloys when the Ti content is about 2.7wt.%, which results in decreased stress-rupture life. But the precipitate of η-Ni3Ti does no harm to the room temperature tensile properties.