Processing map-microstructure evolution correlation of hot compressed near alpha titanium alloy (TiHy 600)

Hot compression tests on TiHy 600 alloy (equivalent to IMI 834) is performed using Gleeble-3800((R)) thermo-mechanical simulator. The hot deformation behavior of TiHy 600 alloy is characterized on the basis of flow stress variation with true stress-true strain curves at different strain rates ranging from 10(-3) s(-1) to 10 s(-1) and hot deformation temperatures ranging from 900 degrees C to 1050 degrees C, with maximum engineering strain up to 50%. The flow stress is found to be strongly dependent on deformation temperature, strain rate and strain, and it decreases with increasing temperature and decreasing strain rate. The flow curves at various temperatures and strain rates also showed dynamic recrystallization process at temperature range (900 degrees C-975 degrees C) in all strain rates and dynamic recovery process at high temperature range (1000 degrees C and above) in all the strain rates. Using flow stress values from the true stress-true strain curves and by applying dynamic material modeling approach, processing maps are developed at various true strains of 0.3, 0.4, 0.5 and 0.6. Processing maps exhibited safe and unsafe domains with varying efficiency of power dissipation values. Safe and unsafe domains at 0.6 strain are derived from their flow curves are correlated with its related microstructures and misorientation distribution profiles. Hot compression at 900 degrees C (alpha-rich region) mostly resulted into new fine dynamic recrystallized equiaxed alpha grains along grain boundaries of large deformed alpha grains. Higher temperature (950 degrees C-975 degrees C) compression in the (alpha+beta) region generated mixture of deformed large alpha grains containing subgrain boundaries and secondary alpha laths generates from deformed beta. Further compression at higher temperature (1000 degrees C -beta-rich region and 1050 degrees C -single beta region) resulted in the formation of secondary alpha laths from deformed beta with few equiaxed alpha grains at 1000 degrees C sample only. The misorientation profile of alpha phase corroborates with the deformation mechanism in a region through its equiaxed alpha grains and in beta region through its secondary alpha variant laths misorientations. (C) 2016 Published by Elsevier B.V.