Enhanced high temperature performance of two-scale network-structured (TiB+Ti5Si3)/TA15 composites by simultaneous adjustment of matrix and nano-scaled Ti5Si3

To improve the high temperature performance of the titanium matrix composite, solution and aging treatments were carried out on the (TiB + Ti5Si3)/TA15 composite with a two-scale network structure. The microstructure evolution during the heat treatment and high temperature performance at 650 degrees C were investigated. It is found that a fine matrix with basket-weave structure and nano-scaled Ti5Si3 can be obtained through a proper combination of solution and aging treatment. Optimal high temperature performance is achieved with yield strength and ultimate tensile strength improved by 15 % and 24 % respectively without sacrificing ductility. Matrix refinement is attributed to network-distributed TiB and fine martensite after solution treatment. During subsequent aging, fine secondary alpha phase and beta phase are formed and then grow. The growth mechanisms of the secondary alpha phase and beta phase are phase boundary migration and grain coalescence. The main strengthening mechanisms are boundary strengthening of the matrix and the precipitation strengthening of Ti5Si3, which are mainly related to the thickness of the secondary alpha phase and the fraction of Ti5Si3, respectively.