Effects of first-scale TiBw on secondary-scale Ti5Si3 characteristics and mechanical properties of in-situ (Ti5Si3d+TiBw)/Ti6A14V composites

In order to further improve mechanical properties, Ti6A14V matrix composites reinforced with secondary-scale Ti5Si3 particles and first-scale TiB whiskers were designed and prepared by reaction hot pressing. The effects of first-scale TiBw fractions on secondary-scale Ti5Si3 microstructure characteristics and mechanical properties of two-scale network structured composites were investigated. With increasing TiBw fractions, the size of Ti5Si3 particles in beta phase increased, the quantity of Ti5Si3 particles near TiBw reinforcement increased and the morphology changed from isolated particles to interconnected particles. These changes resulted in that the room and high temperature tensile strength of the composites increased, moreover, the creep resistance of the composites improved. Compared with the Ti6A14V alloy, the room and high temperature tensile yield strength of the composites with 3.4 vol% TiBw increased by 36.5%. and 70%, and the elongation remained at 5.0% and 11.5%, respectively. The composites possess approximately one order of magnitude lower steady-state creep rate and about eight times higher time-to-rupture at 873 K/200 MPa. The superior tensile and creep properties can be attributed to adjustment of secondary-scale Ti5Si3 characteristics and two-scale network structure. (C) 2017 Elsevier B.V. All rights reserved.