Mechanical properties and microstructure changes of a new developed 718 alloy after long-time aging at 680℃
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摘要: 利用SEM和TEM研究了一種新型718合金在680℃長期時效至1000h后的組織變化.結果表明:標準合金的主要強化相為γ″,而新合金的主要強化相中除γ″外,γ'的質量分數大幅度增加,呈現出特殊的包覆組織形貌;在長時時效過程中,新型合金具有良好的組織穩定性.新型合金與標準合金的晶界δ相形貌也不盡相同,新合金中為均勻的短棒狀或顆粒狀,標準合金中為針狀或板條狀.兩種合金的室溫和680℃拉伸性能無顯著差別,但新型合金的持久和蠕變性能遠優于標準合金.與標準合金相比,新合金在680℃具有良好的力學性能與組織穩定性.Abstract: SEM and TEM were employed to study the structure stability of a new developed 718 alloy after aging at 680℃ for 1000 h. The results indicate that the main strengthening phase in a standard alloy 718 is γ″, while it is γ″ precipitated on increasing amount γ' in the new developed alloy and a compact morphology forms. The new developed alloy was proved to be very stable after long-time aging at 680℃. The morphology of phase on grain boundary in the standard alloy is long needle-like or lamellar while it is short rod-shaped or granular in the new developed alloy. The tensile properties of the two alloys at room temperature and 680℃ have a slight difference but the stress rupture and creep properties of the new developed alloy are greatly superior to the standard alloy. In comparison with the standard alloy, the new developed alloy has a better combination of mechanical properties and microstructure stability at 680℃.
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Key words:
- 718 alloy /
- long-time aging /
- microstructure /
- mechanical properties /
- creep properties
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