Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7882660 | Acta Materialia | 2014 | 11 Pages |
Abstract
A Co-Cr-Mo alloy with a single ε (hexagonal close-packed, hcp) phase exhibits excellent tensile properties with a 0.2% proof stress of 630 MPa, an ultimate tensile stress of 1072 MPa and an elongation to fracture of 38.3%. The dominant deformation modes are basal ãaã slip and prismatic ãaã slip, and the apparent respective critical resolved shear stresses at room temperature are calculated to be 184 and 211 MPa. This simultaneous activation of both ãaã slips can be explained in terms of the lattice constant ratio c/a of 1.610. There is a tendency for the geometrically necessary dislocations (GNDs) to accumulate at grain boundaries, and the magnitude of this GND accumulation at a particular boundary is dependent on its character. Numerical analysis using a dislocation-model-based strain gradient crystal plasticity calculation makes it possible to characterize the distributions of dislocation density, local stress and local strain in the polycrystalline ε Co-Cr-Mo alloy, and the calculation is largely consistent with the experimental results. This simulation reveals that the activity of the prismatic ãaã slip in addition to the basal ãaã slip contributes to the stress relaxation at the boundary. For this reason, excellent tensile ductility is obtained in the polycrystalline ε Co-Cr-Mo alloy.
Related Topics
Physical Sciences and Engineering
Materials Science
Ceramics and Composites
Authors
Hiroaki Matsumoto, Yuichiro Koizumi, Tetsuya Ohashi, Byong-Soo Lee, Yunping Li, Akihiko Chiba,