High temperature deformation behavior of Ti–46Al–2Cr–4Nb–0.2Y alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 539; pp. 107 - 114
• Main Authors: Kong, Fantao, Chen, Yuyong, Zhang, Deliang, Zhang, Shuzhi
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 30-03-2012; Elsevier
• Subjects: Applied sciences; Deformation; Elasticity. Plasticity; Exact sciences and technology; Forging; Intermetallics; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Microstructure; Processing map; TiAl alloys; Intermetallics; Forging; Processing map; TiAl alloys; Deformation; Microstructure; Hot deformation; Titanium alloy; Plastic flow; Dynamical recrystallization; Aluminium alloy; High temperature; Grain boundary migration; Compression test; Cast alloy; Kinetic equation; Rate equation; Activation energy; Flow stress; Strain rate
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2012.01.066

► Processing map of Ti–46Al–2Cr–4Nb–0.2Y alloy at true strain of 0.5 was established. ► The fraction of recrystallized grains increased with increasing the deformation T. ► Optimized hot processing parameters were determined based on the processing map.
The hot deformation characteristics of cast and hot isostatically pressed Ti–46Al–2Cr–4Nb–0.2Y (at%) alloy in the temperature range of 1100–1250°C and strain rate range of 0.01–1.0s−1 using hot compression tests were studied. The processing map of the alloy at true strain of 0.5 was also developed on the basis of the dynamic materials model (DMM). The experimental results show that the flow stress decreases significantly with increasing deformation temperature and decreasing strain rate. Using the kinetic rate equation the stress exponent n and the apparent activation energy of deformation Q were determined as 4.47 and 400.4kJmol−1, respectively. The efficiency values of power dissipation of the domain at strain rate below 0.4s−1 show that the dynamic recrystallization occurring of γ phase in the alloy is easier in the wide deformation temperature range (1100–1250°C) due to low stacking fault energy. The fraction of new recrystallized grains increased with increasing the hot deformation temperature at a given strain rate. With the increasing of strain rate, the uniformity of microstructure was decreased. The domain defined by the temperature range of 1200–1230°C and the strain rate range of 0.01–0.05s−1 which corresponds to a peak efficiency of about 60% is the optimal deformation condition of the alloy. Based on the optimal deformation conditions, a cylindrical sample was near isothermally forged. The microstructure and shape of pancake by forging was in good agreement with the prediction of processing map.