Structural interpretation of the nucleation and growth of deformation twins in Zr and Ti--1: Application of the coincidence site lattice (CSL) theory to twinning problems in H.C.P. structures
- Los Alamos National Lab., NM (United States)
A step-wise nucleation and growth mechanism based on the coincidence site lattice (CSL) theory is proposed for deformation twinning in h.c.p. structures. Lattice transformation during twinning is accomplished by a coordinated movement of a large number of atoms between two lattice match planes from the matrix to twin positions rather than a layer by layer movement through twinning dislocations as proposed for twinning dislocation theories. The sidewise propagation and thickening of a twin lamella proceeds in a step-wise manner with lattice match planes being the coherent boundaries between the matrix and twins. This model predicts that twinning in h.c.p. lattices can occur at a high velocity close to the sound speed, which is impossible according to twinning dislocation theories. The proposed mechanism is also consistent with other observations such as lack of critical-resolved-shear-stress for twinning, emissary dislocations, and insensitivity to temperature. Dislocation reactions may be involved in twinning although they are, at high stresses, not required.
- OSTI ID:
- 72443
- Journal Information:
- Acta Metallurgica et Materialia, Journal Name: Acta Metallurgica et Materialia Journal Issue: 6 Vol. 43; ISSN 0956-7151; ISSN AMATEB
- Country of Publication:
- United States
- Language:
- English
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