Effect of twin boundaries on the microstructure and mechanical properties of Inconel 625 alloy

The study investigated the effect of twin boundaries on the microstructure and mechanical properties of Inconel 625 alloy during hot/cold deformation and subsequent heat treatment. And further the mechanisms of twin formation and strengthening were discussed. The results show that coarse deformed grains had both a strong Brass orientation {110} < 112 > and a high dislocation density as a result of deformation twinning, while fine recrystallized grains had both a weak Cube orientation {001} < 100 > and a low dislocation density which was attributed to recrystallization. Meanwhile, the deformation twins were formed by the motion of partial dislocation during hot or cold plastic deformation, while annealing twins were formed by growth accidents on a migrating grain boundary during dynamic or static recrystallization. The yield strength (ay) and elongation (epsilon(f)) of the as-cast sample (247 MPa and 41.00%) were significantly increased (366 MPa and 60.00%, 361 MPa and 52.88%) via hot/cold deformation and subsequent heat treated. This result indicates that tailoring the twin boundaries via thermo-mechanical processing can significantly improve strength and ductility of Inconel 625 alloy.