Dissolution-precipitation of the secondary phase particles in copper-rich Cu-Cr alloys during high-pressure torsion

Svetlana N. Faizova 1Ruslan Z. Valiev 2Natalya V. Balabanova 2

1. Institute of Mechanics, Ufa Scientific Center, 71, Prospect Oktybrya, Ufa 450000, Russian Federation
2. Institute of Physics of Advaced Materials, Ufa State Aviation Technical University (IPAM USATU), 12 K. Marx st., Ufa 450000, Russian Federation

Abstract

There exists growing experimental evidence that the SPD may accelerate diffusion and cause decay of a solid solution and precipitation of particles in its process. In their turn, the particles influence the plastic flow of the material. Such an interdependence may have an important effect on the resulting structure refining.

In the present work high-copper Cu-Cr alloy samples were treated with the high-pressure torsion (HPT) at the room temperature. After 5 turns the average grain size become ~ 90 nm and microhardness increases up to 2100 MPa from 620 MPa in the initial state. The decay of a solid solution has been observed. At the early stages of deformation the alignment of precipitation particles along the localized slip planes is evident. With the further development of the plastic flow relatively large (~1-2 μm) particles remaining in the material totally disappear and the number of nanometer sized ones (~10..20 nm) increases. This change may be caused by mechanical fragmentation or by the concurrent process of the particle dissolution. An evidence for the latter case is the significant increase of the microhardness value after post-deformation ageing. It rises from 2100MPa to 2700 MPa, i.e. by 600 MPa. For comparison, the same treatment of the alloy sample without the HPT provides an increase of the microhardness only by 300 MPa. Dissolution of precipitation particles is incompatible with the equilibrium state diagram for the alloy under investigation and may be linked to the local dynamical distortions of crystalline lattice in the process of the intensive deformation.

This work was supported by RBRF grants (projects #06-08-00971 and #07-08-00567.)

 

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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium D, by Svetlana N. Faizova
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-13 16:54
Revised:   2009-06-07 00:44