Feng Hong, Sun Yonggang, Lian Yuzhou, Zhang Shuzhi, Zhang Changjiang, Xu Ying, Cao Peng
College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China.
Department of Chemical and Materials Engineering, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
Materials (Basel). 2020 Dec 16;13(24):5751. doi: 10.3390/ma13245751.
To further improve the mechanical properties of the as-cast 7.5 vol.% TiB/Ti-6Al-2.5Sn-4Zr-0.7Mo-0.3Si composite, multi-directional forging (MDF) and subsequent heat treatments were carried out to adjust TiB whiskers (TiB) and matrix characteristics. The effect of various microstructures on the tensile properties and fracture toughness of the composites was analyzed in this paper. After MDF, the TiB are broken into short rods with a low aspect ratio and display a random distribution. Moreover, distinct microstructures were obtained after thermomechanical processing and different heat treatments. Both room-temperature and high-temperature tensile strength and ductility are improved after thermomechanical processing. By increasing the solution-treatment temperature, the microstructures transform from equiaxed to fully lamellar. A simultaneous improvement of the room-temperature and high-temperature properties is associated with the microstructural changes. In addition, the fracture toughness exhibits an increasing trend as the volume fraction of equiaxial α phases decreases. The lamellar microstructure demonstrates excellent fracture toughness due to deflection of the crack propagation path.
为进一步提高铸态7.5体积%TiB/Ti-6Al-2.5Sn-4Zr-0.7Mo-0.3Si复合材料的力学性能，进行了多向锻造（MDF）及后续热处理，以调整TiB晶须（TiB）和基体特性。本文分析了各种微观结构对复合材料拉伸性能和断裂韧性的影响。多向锻造后，TiB断裂成低长径比的短棒并呈随机分布。此外，热机械加工和不同热处理后获得了不同的微观结构。热机械加工后，室温及高温拉伸强度和延展性均得到提高。通过提高固溶处理温度，微观结构从等轴转变为完全片状。室温及高温性能的同时提高与微观结构变化有关。此外，随着等轴α相体积分数的降低，断裂韧性呈上升趋势。由于裂纹扩展路径的偏转，片状微观结构显示出优异的断裂韧性。
