Effects of Solid-Solution Treatment on Microstructure and Mechanical Properties of HIP Treated Alloy 718

The aim of this study is to explore alloy 718 that treated at an optimal HIP process, and then imposed various solid-solution temperatures and aging treatment. The experimental results indicated that Laves and δ precipitations obviously appeared within the grain boundary, under HIP treatment and lower solid-solution temperatures (940°C), which would result in poor mechanical properties. However, Laves and δ phase can be completely dissolved at 1020°C 1 hour solid-solution treatment. The tensile strength was increased to 1331.5 MPa, and elongation reached up to 6.1% under a 1020°C solid-solution and aging treatment. Increasing the solid-solution temperature to 1060°C would cause parts of the NbC to dissolve, thus a large number of the thin sheet-shaped NbC would appear in the solid-solution and aging specimen. The yield stress is slight increase, but a lot of NbC precipitations will result in the decreasing tensile strength (1298.8 MPa) and elongation (5.4%). As a result, the optimal solid-solution treatment parameter of alloy 718 is 1020°C for 1-hour.