Study on the thermal deformation behavior and microstructure of FGH96 heat extrusion alloy during two-pass hot deformation

The change rules associated with hot deformation of FGH96 alloy were investigated by isothermal two-pass hot deformation tests in the temperature range 1050-1125℃ and at strain rates ranging from 0.001 to 0.1 s^-1 on a Gleeble 3500 thermo-simulation machine. The results showed that the softening degree of the alloy between passes decreases with increasing temperature and decreasing strain rates. The critical strain of the first-pass is greater than that of the second-pass. The true stress-true strain curves showed that single-peak dynamic recrystallization, multi- peak dynamic recrystallization, and dynamic response occur when the strain rate is 0.1, 0.01, and 0.001 s^-1, respectively. The alloy contains three different grain structures after hot deformation:partially recrystallized tissue, completely fine recrystallized tissue, coarse-grained grains. The small-angle grain boundaries increase with increasing temperature. Increasing strain rates cause the small-angle grain boundaries to first increase and then decrease.