Microscopic mechanism of plastic deformation in a polycrystalline Co-Cr-Mo alloy with a single hcp phase

作者：Matsumoto Hiroaki^*; Koizumi Yuichiro; Ohashi Tetsuya; Lee Byong Soo; Li Yunping; Chiba Akihiko

来源：Acta Materialia, 2014, 64: 1-11.

DOI：10.1016/j.actamat.2013.11.005

• Cobalt-chromium-molybdenum alloy
• Deformation mode
• Dislocation slip
• Crystal plasticity analysis
• Geometrically necessary dislocations

A Co-Cr-Mo alloy with a single a (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 < a > slip and prismatic < a > 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 < a > 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 epsilon Co-Cr-Mo alloy, and the calculation is largely consistent with the experimental results. This simulation reveals that the activity of the prismatic < a > slip in addition to the basal < a > slip contributes to the stress relaxation at the boundary. For this reason, excellent tensile ductility is obtained in the polycrystalline epsilon Co-Cr-Mo alloy.

• 出版日期2014-2