In-Plane Anisotropy in Mechanical Behavior and Microstructural Evolution of Commercially Pure Titanium in Tensile and Cy
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COMMERCIALLY pure titanium is a candidate material for various structural applications in aerospace, biomedical, and chemical industries due to its higher specific strength, good formability, and superior corrosion resistance. Tensile behavior of commercially pure titanium (cp-Ti) has been studied in detail,[1–5] and recently, many investigations focusing on in-plane anisotropy of tensile properties of cp-Ti have been carried out.[6–11] Bathini et al.[6] carried out tensile and cyclic tests on rolled sheets of cp-Ti and showed that the samples obtained along the longitudinal (rolling) direction exhibit higher elastic modulus, yield strength, and tensile strength as well as marginally higher elongation to failure and reduction in area compared to the transverse direction (TD) sample. In contrast, stress-controlled high cycle fatigue tests showed higher cyclic life for transverse orientation than longitudinal orientation. On the other hand, Hama and co-workers[8,9] found that in cp-Ti Grade 1 and Grade 2 sheets,
SUBHASIS SINHA and N.P. GURAO are with the Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208016, India. Contact email: [email protected] Manuscript submitted February 25, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
the TD-oriented specimen shows the highest yield strength while the rolling direction (RD)—oriented specimen exhibits the highest tensile strength. In addition, they showed that the 45 deg—oriented specimen exhibits the highest total elongation and that the anisotropy in mechanical properties is higher in Grade 1 titanium compared to Grade 2 titanium. In this context, the present authors studied the influence of initial texture on tensile behavior of cp-Ti,[12,13] where three different orientations from different planes (normal direction (ND), RD, and TD) of as-received plate were used. Subsequently, the cyclic behavior of two distinct orientations (out of the three) was also studied.[14] However, it is desirable that a systematic study on tensile (and tension-compression cyclic) deformation and texture should have only the direction changing and not the plane. Such an investigation is more suited for uniaxial tension (or tension-compression), where only one direction is important. The influence of specimen orientation within the same plane is important because in-plane anisotropy is significant even in cubic materials and is expected to be higher in hexagonal-close-packed (hcp) materials. For this reason, earlier authors have studied anisotropy of various properties in cp-Ti.[15–19] Nixon et al.[15] carried out experimental studies and constitutive modeling of quasi-static tension and compression tests on RD- and TD-oriented specimens of a-Ti. They observed the nonsymmetric and orthotropic mechanical response
of titanium with the hardening rate strongly influenced by the loading direction and sense of applied load. Moreno-Valle et al.[16] found significant anisotropy in both uniaxial and biaxial deformation of cp-Ti after hydrostatic extrusion. C
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