Effects of first-scale TiBw on secondary-scale Ti5Si3 characteristics and mechanical properties of in-situ (Ti5Si3+TiBw)/Ti6Al4V composites

Abstract In order to further improve mechanical properties, Ti6Al4V matrix composites reinforced with secondary-scale Ti 5 Si 3 particles and first-scale TiB whiskers were designed and prepared by reaction hot pressing. The effects of first-scale TiBw fractions on secondary-scale Ti 5 Si 3 microstructure characteristics and mechanical properties of two-scale network structured composites were investigated. With increasing TiBw fractions, the size of Ti 5 Si 3 particles in β phase increased, the quantity of Ti 5 Si 3 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 Ti6Al4V 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 Ti 5 Si 3 characteristics and two-scale network structure.