On the mechanisms of superplasticity in Ti–6Al–4V

Superplastic Property of the Ti–6Al–4V Alloy with Ultrafine‐Grained Heterogeneous Microstructure

“…[2] In fact, refining the microstructure of Ti-64 alloy has resulted in excellent superplastic property associated with frequent occurrence of grain boundary sliding (GBS). [3][4][5][6][7][8] Quite recently, Alabort et al [9] and Zherebtsov et al [10] have reported superplastic behavior of Ti-64 alloy in detail. In order to enhance superplastic properties, it requires frequent activation of accommodation mechanism of stress concentration.…”

“…Furthermore, the role of the ultrafine-grained-equiaxedmicrostructure on deformation process associated with an occurrence of superplasticity has been mentioned in detail. [5,9,10] To summarize this work, it can be emphasized that the GBS and accommodation mechanisms (caused by DRX and dynamic b precipitation at boundaries) are optimally activated (under the lowtemperature-superplasticity at the specific-strain-rate-condition) by optimizing the starting microstructure, so as to have an ultrafinegrained heterogeneous microstructure composed of fine equiaxed a-grains and fine lamellar a-grains. Herein, frequent activation of accommodation mechanisms in the ultrafine-grained heterogeneous starting microstructure is of particular importance.…”

Evolution of Microstructure and Residual Stress in Hot Rolled Ti-6Al-4V Plates Subjected to Different Heat Treatment Conditions

“…The deformation in Ti alloys is complex due to the inherent thermal and mechanical anisotropy of the constituent phases. Furthermore, in the temperature range of interest (600°C -950°C), the material undergoes a reversible -phase transformation, which can contribute to stress relaxation [2].…”

“…The diffraction peak at a Bragg angle of 140 o , corresponding to the {211} crystallographic plane in the phase, was used to calculate residual strain which was then converted to residual stress, assuming a Young's Modulus of 118 GPa and Poisson's Ratio of 0.342. Although Ti-6Al-4V is a dual phase alloy, it consists of approximately 92% phase at room temperature and therefore the stress associated with the phase is assumed to have a minimal effect on the overall residual stress magnitude [2]. Nine measurements were performed on the top surface of each plate at increments of 25 mm from the plate center position, with three measurements along the base at increments of 50 mm from the center.…”

“…The deformation in Ti alloys is complex due to the inherent thermal and mechanical anisotropy of the constituent phases. Furthermore, in the temperature range of interest (600°C -950°C), the material undergoes a reversible -phase transformation, which can contribute to stress relaxation [2].Thus, it is imperative that the evolution of residual stress is understood when designing and modifying microstructure for high value, critical aerospace components. The aim of this work was to evaluate microstructure and the through-thickness residual stress distribution induced by thermo-mechanical and subsequent industrial heat treatment processing of 38 mm Ti-6Al-4V plate, using multiple residual stress measurement techniques.…”