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2572681 
Journal Article 
Allotropic phase transformation of pure zirconium by high-pressure torsion 
Edalati, K; Horita, Z; Yagi, S; Matsubara, E 
2009 
1 
Materials Science and Engineering A: Structural Materials Properties Microstructure and Processing
ISSN: 0921-5093
EISSN: 1873-4936 
523 
1-2 
277-281 
WOS:000270632900041 
Pure Zr is processed by high-pressure torsion (HPT) at pressures in the range of 1-40 GPa. A phase transformation occurs from alpha to omega phase during HPT at pressures above similar to 4 GPa while the total fraction of omega phase increases with straining and saturates to a constant level at higher strain. This phase transformation leads to microstructural refinement, hardness and strength enhancement and ductility reduction. Lattice parameter measurements confirm that c for alpha phase is expanded about 0.6% by the presence of omega phase. The temperature for reverse transformation from omega to alpha phase increases with straining and thus, straining under high pressure increases thermal stability of omega phase. The omega phase obtained by HPT is stable for more than 400 days at room temperature. (C) 2009 Elsevier B.V. All rights reserved. 
Zirconium; High-pressure torsion; Severe plastic deformation; Omega phase; Phase transformation; Allotropic transformation