A COMPARISON OF EXPERIMENTAL AND COMPUTER-SIMULATED ISOTHERMAL UPSET FORGING OF IMI685 TITANIUM-ALLOY

The deformation characteristics of IMI685 titanium alloy in unlubricat ed-die upset forging under isothermal conditions have been investigate d in both the beta and (alpha + beta) phase fields in the temperature ranges 1025-1075 degrees C and 950-1000 degrees C respectively and in the strain rate range 0.09-0.005 s(-1). Finite-element methods were us ed with a finite-element code, ABAQUS, to simulate the deformation pro cesses and analyse the deformation distribution of the specimens. The deformation distribution and microstructural features of the deformed specimens were also studied by optical and electron metallography. The deformation patterns obtained from finite-element analysis are in goo d agreement with those obtained from metallography. Undeformed grains and grains with little deformation were observed in areas coinciding w ith regions having lower values of the effective plastic strain in fin ite-element analysis. In areas in which higher values of the effective plastic strain were obtained, the structure featured elongated grains for beta forged specimens and spheroidized alpha grains for (alpha beta) forged specimens. However, changing the strain rate did not appe ar to have a major influence on the deformation distribution in either of the phase fields studied. It was also concluded that the degree of inhomogeneous deformation in beta forging is much lower than that in (alpha + beta) forging.