Ti-Cu-Ni alloys with high strength and good plasticity

The Ti50Cu50-xNix (x = 18, 25,40) alloys with 2 mm in diameter fabricated by copper mold casting method are investigated in terms of microstructure, mechanical properties and fracture behavior. The Ti2Cu particle phase and Ti(Cu,Ni) dendritic phase are distributed in the TiNi0.8Cu0.2 matrix for Ti50Cu32Ni18 alloy, which exhibits high yield strength but very low plasticity. While the microstructures for both Ti50Cu25Ni25 and Ti50Cu10Ni40 alloys show Ti(Cu,Ni) dendritic phase embedded in the TiNi0.8Cu0.2 matrix. Both of the alloys with the higher Ni content exhibit lower yield strength and better plasticity, showing that the plasticity of the alloys was much improved by increasing Ni content. The Ti50Cu10Ni40 alloy exhibits two obvious yielding behaviors during compression. The first yielding point is at 780 MPa, and the second at 2000 MPa. The ultimately compressive fracture strength and elongation of this alloy are of 2240 MPa and 2.5%, respectively. (C) 2007 Elsevier B.V. All rights reserved.