Metallurgical and Materials Transactions A

, Volume 43, Issue 3, pp 977–985 | Cite as

Mechanisms and Kinetics of Static Spheroidization of Hot-Worked Ti-6Al-2Sn-4Zr-2Mo-0.1Si with a Lamellar Microstructure

  • Chan Hee Park
  • Jong Woo Won
  • Jin-Woo Park
  • S. L. Semiatin
  • Chong Soo Lee
Article

Abstract

The effect of imposed strain ε, annealing temperature T A, and annealing time τ on the static spheroidization behavior of Ti-6Al-2Sn-4Zr-2Mo-0.1Si having an initial lamellar microstructure was investigated. For this purpose, the samples were compressed isothermally at 1173 K (900 °C) to ε = 1.0 and subsequently annealed at 1228 K (955 °C) ≤ T A ≤ 1253 K (980 °C) for 10 minutes ≤ τ ≤ 24 hours. For each test condition, metallography was performed to evaluate the change in aspect ratio (AR) and thus quantify the structural evolution from a lamellar to an equiaxed morphology. The average AR decreased rapidly during short annealing times as a result of sub-boundary–induced boundary splitting, but it decreased at a considerably slower rate during subsequent long-time, diffusion-controlled termination migration. The overall time to complete the static globularization was thus governed largely by termination migration. To model the observations, a kinetic equation describing the static spheroidization of two-phase titanium alloys was developed. A comparison of experimental results and predictions showed that the model can provide a reasonable prediction of the time required to complete diffusion-controlled migration of the edges of thin lamellar fragments that are circular or elliptical in shape.

Keywords

Lamellar Microstructure Beta Phase Alpha Phase Terminal Solid Solution Broad Face 

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Copyright information

© The Minerals, Metals & Materials Society and ASM International 2011

Authors and Affiliations

  • Chan Hee Park
    • 1
  • Jong Woo Won
    • 2
  • Jin-Woo Park
    • 3
  • S. L. Semiatin
    • 4
  • Chong Soo Lee
    • 2
  1. 1.Advanced Materials Research & Implementation CenterKorea Institute of Materials ScienceChangwonRepublic of Korea
  2. 2.Department of Materials Science and EngineeringPohang University of Science and TechnologyPohangRepublic of Korea
  3. 3.Department of PeriodontologySchool of Dentistry, Kyungpook National UniversityDaeguRepublic of Korea
  4. 4.Air Force Research Laboratory, AFRL/RXLMWright-Patterson AFBUSA

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