Microstructures and fracture toughness of Ti-(43-48)Al-2Cr-2Nb prepared by electromagnetic cold crucible directional solidification

摘要

In the present paper, the microstructures of directionally solidified Ti-(43-48)Al-2Cr-2Nb alloys prepared by electromagnetic cold crucible directional solidification technique were studied in detail. The results show that with the decrease of Al content, the interlamellar spacing of α_2/γ decreases, but the volume fraction of B_2 phase increases. In addition, the fracture toughness of these alloys with different lamellar orientation was investigated by single edge notched beam three-point bending test (SENB). It is revealed that B_2 phase has greatly impacted on the fracture toughness. When the laminates are perpendicular to the loading stress, the increasing of B_2 phase leads to a lower fracture toughness value. On the contrary, B_2 phase becomes barriers for crack propagations and increases fracture toughness value when the laminates are parallel to the loading stress.