Formation of a shock deformation induced ω phase in Zr 20 Nb alloy

• Published in: Acta materialia 2004-10, Vol.52 (18), p.5243-5254
• Main Authors: Dey, G.K., Tewari, R., Banerjee, S., Jyoti, G., Gupta, S.C., Joshi, K.D., Sikka, S.K.
• Format: Article
• Language: English
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; HREM; Martensite; Martensitic transformations; Materials science; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Shock deformation; Transmission electron microscopy; Zr–Nb alloy
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2004.07.008

The formation of a plate shaped ω phase in Zr–Nb alloy after shock deformation has been studied with a view to ascertaining the nature of this transformation. The orientation relationship between the β and the ω lattices was {1 1 1} β//(0 0 0 1) ω and 〈 1 1 ¯ 0 〉 β / / 〈 1 1 2 ¯ 0 〉 ω which is identical to that seen in case of ω phase forming in this alloy on thermal treatment. The experimentally determined habit plane of the plate shaped ω phase has been compared with that predicted from the phenomenological theory of martensite formation. A mechanism of transformation involving shear on the 〈1 1 2〉 planes has been considered. The importance of mechanical instability of the β phase in bringing about this transformation has been investigated. The mechanism of initiation of ω transformation has been ascertained by high resolution electron microscopy (HREM) of the β lattice and compared with that happening during ω formation in the same alloy by thermal treatment.