Characteristics of lamellar evolution and softening behavior of Powder-HIPed TNM alloy during hot compression

The TNM alloy with full lamellar microstructure and extremely less content of beta o/beta phase was prepared by powder hot isostatic pressing technology, and the lamellar evolution during hot compressions at temperature of 1200 degrees C and strain rate of 0.01 s-1 were studied in depth. The results show that massive lamellar colonies kink and bend at the initial stage of compression, called geometric softening, leading to the appearance of shaper stress peak in flow curve. The kinked and bent lamellar colonies result from the continuous rotation of lamellae with the lattice rotation axis of (1120)alpha//(110)gamma, which gradually transfer the angle of the interfaces of lamellar with respect to the loading axis from 0 degrees to 45 degrees. And then recrystallized grains form at kink bands and the boundaries of deformed lamellar colonies, which is responsible for the slow softening kinetics and the persistent softening stage. The absence of beta phase transfers the softening mechanism at the initial deformation stage and weakens the effect of softening at the strain of 0.9.