Enhancing the compressive and tensile properties of Ti-based glassy matrix composites with Nb addition

Combining copper mold suction-casting and copper mold pouring-casting techniques, in-situ Ti-based bulk metallic glass matrix composites (Ti0.45Zr0.31Be0.17Cu0.07)100 − xNbx (x = 4, 6, 8 and 10) with Φ = 3 mm and composites (x = 6, 8 and 10) with Φ = 8 mm are fabricated in order to perform compressive and tensile tests, respectively. The volume and size of crystalline β-Ti(Zr, Nb) dendrites of these composites increase with the increasing Nb content, resulting in the improvement of compressive and tensile properties of the composites. Among these composites, Ti40.5Zr27.9Be15.3Cu6.3Nb10 (x = 10) has the highest compressive ultimate strength of 2756 MPa and plastic strain of 39.5%; meanwhile, it possesses a high tensile ultimate strength of 1428 MPa and a large tensile plasticity of 7.7%. As indicated by the SEM micrographs, in compressive tests, the more branched the dendrites, the more shear bands, and the higher compressive strength and plasticity of these composites. In tensile tests of Ti40.5Zr27.9Be15.3Cu6.3Nb10 (x = 10), ductile fracture features, including the macroscopic necking, fracture of ligament, vein patterns and sliding traces, are observed. The reason of the excellent mechanical properties of the measured composites is that the propagation of shear bands and cracks are impeded by β-Ti(Zr, Nb) dendrites, and then be confined in a small space.