Microstructure and properties of modified and conventional 718 alloys
(1.辽宁省沈阳市东北大学材料与冶金学院
2.辽宁省沈阳市科学院金属研究所
3.Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
4.Central Iron and Steel Research Institute, Beijing 100081, China
5.University of Science and Technology Beijing, Beijing 100083, China
6.School of Materials and Metallurgy, Northeastern University, Shenyang 110006, China
7.Institute of Metal Research, The Chinese Academy of Sciences, Shenyang 110016, China)
2.辽宁省沈阳市科学院金属研究所
3.Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
4.Central Iron and Steel Research Institute, Beijing 100081, China
5.University of Science and Technology Beijing, Beijing 100083, China
6.School of Materials and Metallurgy, Northeastern University, Shenyang 110006, China
7.Institute of Metal Research, The Chinese Academy of Sciences, Shenyang 110016, China)
Abstract: Continuing the effort to redesign IN718 alloy in order to provide microstructural and mechanical stability beyond 650 ℃, IN718 alloy was modified by increasing the Al, P and B contents, and the microstructure and mechanical properties of the modified alloy were compared with those of the conventional alloy by SEM and TEM. The precipitation of the grain boundaries of the two alloys is different. The Cr-rich phase, Laves phase and α-Cr phase are easily observed in the modified alloy. The γ″ and γ′ phases in the modified alloy are precipitated in a “compact form”. The tensile strengths of the modified alloy at room temperature and 680 ℃ are obviously higher than those of the conventional one. The impact energy of the modified alloy is only about half of that of the conventional alloy. Ageing at 680 ℃ up to 1 000 h lowers the tensile properties and impact energy of both the conventional and modified 718 alloys, except increasing the ductility at 680 ℃. It is concluded that the modified alloy is more stable than the conventional one.
Key words: IN718 alloy; microstructure; mechanical properties