Achieving ultra-high hardness of Ti–3Si-1.5Fe–1Mo alloy via tailoring the in-situ Ti₅Si₃

In this work, ultra-high hardness of 598 HV of Ti–3Si-1.5Fe–1Mo alloy was manufactured via tailoring the in-situ Ti₅Si₃ phases. The manipulation of solution and precipitation as well as the regulation of morphology and distribution of the in-situ Ti₅Si₃ phases were achieved by solution heat treatment and subsequent aging. The average size of Ti₅Si₃ in titanium alloy was reduced from 3.13 μm to 2.39 μm, and the tiny Ti₅Si₃ was dispersed in the grain interior, while the residual rod-like and particle Ti₅Si₃ were distributed at the grain boundaries. The hardness and ultimate compressive strength of the alloys were remarkably increased by 151 HV and 373 MPa, respectively. The improvement of mechanical properties by Ti₅Si₃ evolution was mainly ascribed to the unique regulation of morphology and distribution of Ti₅Si₃ and Si-involved variation in solute. Moreover, the degree of solid solution strengthening of Si element produced by the evolution of Ti₅Si₃ was quantitatively obtained by theoretical calculation of phase diagram.