Low-Temperature Superplasticity of Ultra-Fine-Grained Ti-6Al-2Sn-4Zr-2Mo-0.1Si Alloy
Abstract
This study aimed to achieve low-temperature superplasticity of Ti-6Al-2Sn-4Zr-2Mo-0.1Si alloy utilizing dynamic globularization, and to elucidate the deformation mechanisms in the context of inelastic-deformation theory. The as-received microstructure with equiaxed-alpha grain/particle size of 13microneters was refined to 2.2 micronmeters by dynamic globularization at 775 C, which was confirmed by electron back-scattered diffraction (EBSD) analysis. Uniaxial tension tests were carried out for both coarse (starting material) and fine (dynamically globularized materials) grained materials at strain rate range of 10-4 ~ 10-2 s-1 and temperature range of 650 to 750 C. The total elongation of fine grained microstructure (382-826 %) was considerably enhanced as compared to that of coarse grained microstructure (189-286 %) at 10-4 s-1. With respect to the microstructural evolution, the dynamic coarsening rate of alpha phase during deformation was ~12 times faster than that of static coarsening, and both static and dynamic coarsening rate for Ti-6Al-2Sn-4Zr-2Mo-0.1Si alloy were ~2 to 4 times lower than those for Ti-6Al-4V alloy, which was attributed to lower diffusivity of rate-limiting solute at the similar test temperature. It was found that the mechanism of the low-temperature superplasticity of Ti-6Al-2Sn-4Zr-2Mo-0.1Si alloy was grain boundary sliding (GBS) accommodated by dislocation motion with both stress exponent (n) and grain size exponent (p) values of ~2. When the alpha grain/particle size was considered to be an effective grain size, the apparent activation energy for low temperature superplasticity of Ti-6Al-2Sn-4Zr-2Mo-0.1Si alloy (~169 kJ/mol) was close to that of Ti-6Al-4V alloy (~160 kJ/mol).
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 31, 2009
- Accession Number
- ADA497273
Entities
People
- Chan H. Park
- Chong S. Lee
Organizations
- Pohang University of Science and Technology