Hot Deformation Behavior and Processing Map of a Novel Ti750s High-Temperature Titanium Alloy

Abstract

Ti750s titanium alloy, a novel high-temperature titanium alloy designed for short-term service at elevated temperatures (700–750 °C), has previously lacked comprehensive understanding of its hot processing behavior. In this study, the high-temperature deformation behavior and microstructural evolution of the Ti750s alloy were systematically investigated through thermal simulation compression tests conducted at temperatures ranging from 900 to 1070 °C and strain rates between 0.1 and 10 s⁻¹. A hot processing map was constructed using the dynamic material model to optimize the hot processing parameters. The results indicated that the optimal processing window was between 1040 and 1070 °C with a strain rate of 0.1 s⁻¹. Processing within the instability region resulted in localized plastic deformation, manifesting as pronounced shear bands and a highly heterogeneous strain distribution; this region should be avoided during hot deformation. Within the α + β phase safety zone characterized by low power dissipation rates between 0.32 and 0.4, the primary deformation mechanism in this region was dynamic recovery (DRV), where the lamellar α grains underwent deformation and rotation. Conversely, in the α + β phase safety zone with high-power dissipation rates between 0.45 and 0.52, dynamic spheroidization of the α phase and dynamic recrystallization (DRX) of the β phase occurred concurrently. In the β phase safety zone with low power dissipation rates between 0.32 and 0.51, the primary deformation mechanism consisted of DRV of β grains, accompanied by limited DRX. However, in the β phase safety zone with high-power dissipation rates exceeding 0.56, both DRV and DRX of β grains took place, resulted in a significant increase in the size and number of recrystallized grains compared to those observed under low power dissipation conditions.