ORIGINAL ARTICLE Material characterization, constitutive modelling, and processing map for superplastic deformation region in Ti-6Al-4V alloy M. A. Wahed 1 & A. K. Gupta 1 & V. Sharma 1 & K. Mahesh 2 & S. K. Singh 3 & N. Kotkunde 1 Received: 15 August 2018 /Accepted: 29 May 2019 # Springer-Verlag London Ltd., part of Springer Nature 2019 Abstract Superplastic deformation behavior plays a significant role in the manufacturing of light and complex shaped components, and particularly, the superplastic behavior of Ti-6Al-4Valloy has different fields of applications such as hollow fan blades used in a gas turbine engine and high-performance heat exchangers. To study this, uniaxial tensile tests have been conducted within a temperature range of 700 to 900 °C at different strain rates, 0.01/s, 0.001/s, and 0.0001/s. The test results show more than 50% elongation in general and more than 200% elongation from 750 to 900 °C at 0.0001/s strain rate, representing the superplastic deformation behavior in Ti-6Al-4Valloy. The fractured specimens have been characterized by means of an optical microscope, scanning electron microscope, and X-ray diffraction techniques. Microstructure analysis confirms coarsening of grain size and variation in volume fraction of β with temperature, while SEM study clearly indicates ductile fracture with improved amount of dimples and flow lines at elevated temperatures. X-ray diffraction results indicate that the basic peaks position remains the same, but parameters vary due to superplastic deformation behavior. To accurately estimate the flow stress behavior, modified Arrhenius model has been developed and found to have the correlation coefficient (R) as 0.9939 when compared with experi- mental flow stress. Furthermore, by using the flow stress data, processing maps have been developed for analyzing the super- plastic deformation behavior based on the efficiency and flow instability region at different elevated temperatures and strain rates. Processing maps clearly show excellent efficiency of power dissipation without any presence of flow instability in the super- plastic deformation domain, i.e., from 770 to 900 °C temperature range and at 0.01–0.0001/s strain rate. Keywords Ti-6Al-4Valloy . Superplastic deformation . Material properties . Material characterization . Constitutive modelling . Processing map 1 Introduction Titanium is recognized as the fourth most abundant element that originates from the Earth’ s crust after iron, aluminum, and magnesium. Among titanium alloys, Ti-6Al-4V alloy is note- worthy as it adds 50% of aggregate fabrication and is regarded as the spearhead of the titanium industry [1]. Ti-6Al-4V alloy contains exceptional properties like high melting temperature, strength to weight ratio, and good corrosion resistance; how- ever, its application is restricted up to 400 °C due to the oxi- dation effect at higher temperatures. Ti-6Al-4Valloy is a poly- crystalline material, i.e., it can endure high ductility (El %) of ~ 200% prior to rupture, which is an indication of superplastic behavior. Superplastic behavior is achieved by using fine- grained equiaxed or bimodal structures, at deformation tem- perature approximately half of the melting temperature and with a low strain rate range of 0.0001 – 0.01/s [ 2 ]. Superplastic deformation behavior of Ti-6Al-4V alloy has ap- plications in different fields such as hollow wide-chord fan blades, airframe windows, and high-performance heat exchangers. Over more than a decade, several researchers have investi- gated the superplastic behavior in Ti-6Al-4V alloy from dif- ferent perspectives. Alabort et al. [3] performed tensile tests with constant strain rate on 5-mm-thick Ti-6Al-4Valloy sheets * M. A. Wahed p20150411@hyderabad.bits-pilani.ac.in 1 Department of Mechanical Engineering, BITS-Pilani, Hyderabad Campus, Hyderabad 500078, India 2 Department of Metallurgical and Materials Engineering, RGUKT Basar, Nirmal, Telangana 504107, India 3 Department of Mechanical Engineering, GRIET, Hyderabad 500072, India The International Journal of Advanced Manufacturing Technology https://doi.org/10.1007/s00170-019-03956-z