New insights into the phase transformations to isothermal ω and ω-assisted α in near β-Ti alloys
By Tong Li, D. Kent, G. Sha, L. Stephenson, A. Ceguerra, Simon P. Ringer, Mathew S. Dargusch, J. Cairney. 2016
207 citations recorded by the source corpus.
For multicomponent near-β alloys, we have investigated the mechanisms responsible for the β-to-ω and ω-to-α phase transformations upon isothermal ageing at 573 K. Experimental evidence from atom probe tomography and aberration-corrected high-resolution transmission electron microscopy indicates that the formation of isothermal ω involves a structural reconstruction assisted by nanoscale spinodal decomposition of the β matrix, prior to the specific chemistry change required to form ω, rather than a mixed-mode process with structure and chemistry changes occurring simultaneously as has been previously suggested. First, incommensurate embryonic ω evolve via a displacive mechanism within Mo-lean regions created by second-order coherent spinodal decomposition of the β matrix. The subtle spinodal decomposition in β and chemistry of embryonic ω are carefully analysed by an advanced atom probe data analysis algorithm. When the size of embryonic ɷ exceeds a critical value, commensurate isothermal ɷ forms through the exit of the other alloying solutes. O-rich regions present at the isothermal ω/β interface provide potent sites for the formation of α. The concurrent compositional partitioning of solutes in ɷ and α indicates the transformation from ω to α involves both a rapid lattice reconstruction at the ω/α interface and a slow Al diffusion at the α/β, therefore a mixed-mode displacive-diffusive process. This study provides novel experimental evidence to understand the much-disputed transformation processes and elucidate the mechanisms responsible for these important phase transformations.
Subfields: Biomedical Engineering, Materials Chemistry, Mechanical Engineering
View Paper: https://www.semanticscholar.org/paper/9aaa1a7bd185c84725436e6018a72652d5108e41
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Citations in the corpus
- A Review of Metastable Beta Titanium Alloys (2018, background): “secondary α-phase precipitates during isothermal aging is illustrated [132].”