Thermomechanical Behavior of Commercially Pure Titanium (CP-Ti) During Isothermal Compressive Deformation
The thermomechanical deformation behavior of commercially pure Titanium (CP-Ti) was studied by isothermal compression up to 50 % height reduction of specimen at 773–1273 K with strain rate 0.01–1.0 s−1 with boron nitride as solid lubricant. The influence
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M. Vetrivel, T. Senthilvelan and G. Sriram Abstract The thermomechanical deformation behavior of commercially pure Titanium (CP-Ti) was studied by isothermal compression up to 50 % height reduction of specimen at 773–1273 K with strain rate 0.01–1.0 s−1 with boron nitride as solid lubricant. The influence of Zener-Hollomon parameters, strain, strain rate imposing on the flow stress were analyzed in the high-temperature deformation of CP-Ti in the α + β phase region. The apparent activation energy of deformation calculated to be 343.69 kJ mol−1 and the processing map shows that the dynamic softening is accelerated with increase of deformation temperature and decrease of strain rate, and can be divided into three different regions viz., threestage work hardening, two-stage work hardening, and flow softening. Geometric dynamic recrystallizations were found as a result of strain rate and temperature while describing the grain refinement process of CP-Ti during high-temperature compression. Keywords Zener-Hollomon parameter • Activation energy • Processing map • Commercially pure titanium • Solid lubricant • Dynamic recrystallizations
1 Introduction Commercially pure titanium (CP-Ti) is of great importance in many industrial applications due to its highly attractive properties, such as good deformability at high temperatures, low density, high biocompatibility, and excellent corrosion resistance [1]. It is chemically inert and biologically more compatible than M. Vetrivel (*) · G. Sriram Sri Chandrasekharendra Saraswathi Vishwa MahaVidhalaya, Kanchipuram 631 561, India e-mail: [email protected] T. Senthilvelan Pondicherry Engineering College, Pudhucherry 605014, India
S. Sathiyamoorthy et al. (eds.), Emerging Trends in Science, Engineering and Technology, Lecture Notes in Mechanical Engineering, DOI: 10.1007/978-81-322-1007-8_30, © Springer India 2012
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Ti-6Al-4V, which is currently the material of choice for forming bone-interfacing implants for orthopedic applications. However, it is hard for CP-Ti to strengthen to a level comparable to Ti-6Al-4V [2]; therefore, developing higher strength CP-Ti is an attractive work for medical applications. In order to increase the strength of CP-Ti, grain-size refining is an effective approach, and generally is being carried out from the dynamic recovery to dynamic recrystallizations. Deformation behavior of CP-Ti during cold and hot working has been studied extensively by many researchers [3–9]. Zhipeng Zeng et al. [10, 11] investigated deformation temperatures below the transformation temperature in CP-Ti (Grade II). They recorded stress–strain curve between temperatures 673 and 973 K at strain 0.6, also developed the constitutive equation for CP-Ti. One of the very common industrial processes in the α + β region is superplastic forming, which requires very fine grain sizes and slow speed of deformation [12]. Yong Niu et al. [13] studied the characteristics of superplastic deformation in Ti600 Titanium alloy by recording the stress
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