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Title: Experimental observations elucidating the mechanisms of structural bcc-hcp transformations in {beta}-Ti alloys

Abstract

The formation mechanisms of two hcp {alpha} phase morphologies in Ti-4.5Fe-6.8Mo-1.5Al have been investigated by optical microscopy (OM), atomic force microscopy (AFM), electron probe microanalysis (EPMA) and dilatometry. At relatively high temperatures primary {alpha} forms predominantly on prior bcc {beta} grain boundaries, whereas at lower temperatures so-called bainitic {alpha} plates nucleate both at grain boundaries and intragranularly. This morphological transition with decreasing temperature is associated with a change in transformation mechanism. The combined results of EPMA, OM and dilatometry show that the growth of these bainitic {alpha} plates is partitionless, and not accompanied by a volume change. Subsequently, a post-transformation redistribution of Fe takes place, which causes a dilatation that can be modelled based on the diffusion of Fe and the interface-area density. This mechanism as well as the formed microstructure are similar to bainite in steel, and therefore we chose to denote this transformation product as bainitic {alpha}. In addition, the AFM observations on bainitic {alpha} plates show an invariant plane strain surface relief with tilt angles that are consistent with the Burgers' transformation model based on shear. In contrast, the AFM results show that the formation of primary {alpha} is accompanied by an irregular dip on a freemore » surface, which is in agreement with the volume decrease measured using dilatometry. Furthermore, the EPMA results show that primary {alpha} is formed by a partitioning transformation. The change in transformation mechanism with decreasing temperature is supported by the observed trend in both the dilatation and the volume fraction {alpha} as a function of temperature.« less

Authors:
 [1];  [2]
  1. Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands)
  2. Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands)
Publication Date:
OSTI Identifier:
20853737
Resource Type:
Journal Article
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 74; Journal Issue: 13; Other Information: DOI: 10.1103/PhysRevB.74.134114; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1098-0121
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALUMINIUM ALLOYS; ATOMIC FORCE MICROSCOPY; BAINITE; BCC LATTICES; DIFFUSION; DILATOMETRY; ELECTRON MICROPROBE ANALYSIS; ELECTRON PROBES; GRAIN BOUNDARIES; HCP LATTICES; INTERFACES; MOLYBDENUM ALLOYS; MORPHOLOGY; NUCLEATION; OPTICAL MICROSCOPY; PHASE TRANSFORMATIONS; PLATES; SHEAR; SOLIDS; STRAINS; SURFACES; TEMPERATURE DEPENDENCE; TITANIUM ALLOYS

Citation Formats

Bohemen, S. M. C. van, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, Sietsma, J, and Zwaag, S van der. Experimental observations elucidating the mechanisms of structural bcc-hcp transformations in {beta}-Ti alloys. United States: N. p., 2006. Web. doi:10.1103/PHYSREVB.74.134114.
Bohemen, S. M. C. van, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, Sietsma, J, & Zwaag, S van der. Experimental observations elucidating the mechanisms of structural bcc-hcp transformations in {beta}-Ti alloys. United States. https://doi.org/10.1103/PHYSREVB.74.134114
Bohemen, S. M. C. van, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, Sietsma, J, and Zwaag, S van der. 2006. "Experimental observations elucidating the mechanisms of structural bcc-hcp transformations in {beta}-Ti alloys". United States. https://doi.org/10.1103/PHYSREVB.74.134114.
@article{osti_20853737,
title = {Experimental observations elucidating the mechanisms of structural bcc-hcp transformations in {beta}-Ti alloys},
author = {Bohemen, S. M. C. van and Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft and Sietsma, J and Zwaag, S van der},
abstractNote = {The formation mechanisms of two hcp {alpha} phase morphologies in Ti-4.5Fe-6.8Mo-1.5Al have been investigated by optical microscopy (OM), atomic force microscopy (AFM), electron probe microanalysis (EPMA) and dilatometry. At relatively high temperatures primary {alpha} forms predominantly on prior bcc {beta} grain boundaries, whereas at lower temperatures so-called bainitic {alpha} plates nucleate both at grain boundaries and intragranularly. This morphological transition with decreasing temperature is associated with a change in transformation mechanism. The combined results of EPMA, OM and dilatometry show that the growth of these bainitic {alpha} plates is partitionless, and not accompanied by a volume change. Subsequently, a post-transformation redistribution of Fe takes place, which causes a dilatation that can be modelled based on the diffusion of Fe and the interface-area density. This mechanism as well as the formed microstructure are similar to bainite in steel, and therefore we chose to denote this transformation product as bainitic {alpha}. In addition, the AFM observations on bainitic {alpha} plates show an invariant plane strain surface relief with tilt angles that are consistent with the Burgers' transformation model based on shear. In contrast, the AFM results show that the formation of primary {alpha} is accompanied by an irregular dip on a free surface, which is in agreement with the volume decrease measured using dilatometry. Furthermore, the EPMA results show that primary {alpha} is formed by a partitioning transformation. The change in transformation mechanism with decreasing temperature is supported by the observed trend in both the dilatation and the volume fraction {alpha} as a function of temperature.},
doi = {10.1103/PHYSREVB.74.134114},
url = {https://www.osti.gov/biblio/20853737}, journal = {Physical Review. B, Condensed Matter and Materials Physics},
issn = {1098-0121},
number = 13,
volume = 74,
place = {United States},
year = {2006},
month = {10}
}