Ti-6A1-4V: Deformation Map and Modelisation of Tensile Behavior (Ti-6A1-4V: Vervormingsmechanismen en modelleren van het gedrag bij trek)

Tensile tests have been performedon a superplastic titanium alloy. Different strain rates from 5 10-4s-1 to 5 10-2 s-1 and various temperatures upto 1050°C were explored. The results of these tests, supplemented withmicrostructural investigations allow, as a function of temperature and strainrate, the determination of mechanical properties such as flow stress, strainhardening and fracture strain as well as the identification of mechanisms suchas grain boundary sliding, dynamic recrystallization and dynamic grain growth.A modified Norton-Hoff law is proposed to characterize the tensile behaviour ofthis alloy. All temperature-strain rate combinations have been grouped into anumber of domains, each corresponding to a particular deformation mechanism.For each domain the Norton-Hoff parameters have been determined. Closeagreement between the predicted and experimental stress-strain relationshipshas been achieved.status: publishe

Ti-6Al-4V: Deformation map and modelisation of tensile behaviour

Tensile tests have been performed on a superplastic titanium alloy. Different strain rates from 5 x 10⁻⁴ s⁻¹ to 5 x 10⁻² and s⁻¹ various temperatures up to 1050 °C were explored. The results of these tests, supplemented with microstructural investigations allow, as a function of temperature and strain rate, the determination of mechanical properties such as flow stress, strain hardening and fracture strain as well as the identification of mechanisms such as grain boundary sliding, dynamic recrystallization and dynamic grain growth. A modified Norton-Hoff law is proposed to characterize the tensile behaviour of this alloy. All temperature-strain rate combinations have been grouped into a number of domains, each corresponding to a particular deformation mechanism. For each domain the Norton-Hoff parameters have been determined. Close agreement between the predicted and experimental stress-strain relationships has been achieved.status: publishe

Deformation mechanisms of Ti-6Al-4V during tensile behavior at low strain rate

A superplastic Ti-6Al-4V grade has been deformed at a strain rate of 5 x 10(-4) s(-1) and at temperatures up to 1050 degrees C. Structural mechanisms like grain boundary sliding, dynamic recrystallization, and dynamic grain growth, occurring during deformation, have been investigated and mechanical properties such as How stress, strain hardening,, and strain at rupture have been determined. Dynamic recrystallization (DRX) brings on a decrease in the grain size. This could be of great interest because a smaller grain size allows a decrease in temperature for superplastic forming. For DRX, the driving force present in the deformed microstructure must be high enough. This means the temperature must be sufficiently low to ensure storing of enough dislocation energy but must also be high enough to provide the activation energy needed for DRX and to allow superplastic deformation. The best compromise for the temperature was found to be situated at about 800 degrees C; this is quite a bit lower than the 925 degrees C referenced in the literature as the optimum for the superplastic deformation. At this medium temperature the engineering strain that could be reached exceeds 400%, a value high enough to ensure the industrial production of complex parts by the way of the superplastic forming. Microstructural, EBSD, and mechanical investigations were used to describe the observed mechanisms, some of which are concurrent.status: publishe