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Mechanisms of kinetically-induced fine secondary α-Ti phase formation in a novel as-cast titanium alloy

Published

Author(s)

Zhi Liang, Xuejun Huang, Jiashi Miao, Fan Zhang, James Williams, Alan Luo

Abstract

The phase transformation mechanisms from the body-centered cubic (BCC) β matrix to fine hexagonal close packed (HCP) α precipitates in an as-cast α-β titanium alloy, Ti-6Al-5Fe-0.05B-0.05C (all in mass %), were investigated experimentally and computationally using CALculation of PHAse Diagram (CALPHAD)-based thermodynamic and kinetic models. The discrete distribution of α precipitates was observed in the as-cast alloy with evidence of strong Fe partitioning. Two main size groups of α precipitates and the Fe partitioning were observed by scanning electron microscopy, scanning transmission electron microscopy, and synchrotron-based small-angle X-ray scattering. The hypothesis of Fe-partitioning driven α precipitate nucleation and growth was validated by precipitation simulation using TC-PRISMA with customized thermodynamic and kinetic descriptions. These results suggested a new titanium alloy design route involving high mobility elements (enhancing fine secondary α precipitates) and demonstrated the capability of CALPHAD-based modeling in titanium alloy design.
Citation
Metallurgical Transactions A-Physical Metallurgy and Materials Science

Keywords

Titanium alloy, microstructure, X-ray scattering, Calphad, alloy design

Citation

Liang, Z. , Huang, X. , Miao, J. , Zhang, F. , Williams, J. and Luo, A. (2022), Mechanisms of kinetically-induced fine secondary α-Ti phase formation in a novel as-cast titanium alloy, Metallurgical Transactions A-Physical Metallurgy and Materials Science, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=933753 (Accessed November 26, 2022)
Created August 16, 2022, Updated August 30, 2022