Spark plasma sintering synthesis of intermetallic T2 in the Mo–Si–B system

Mo5SiB2 (T2) was synthesized by sparking plasma sintering (SPS) under different heating rates and sintering temperatures. The powder mixture with a T2 composition (Mo–12.5Si–25B (at.%)) failed to produce the T2 single-phase alloy due to the volatilization of Si during SPS process. Extra 0.5 at.% Si added to this mixture offset the volatilization loss. It has been found that heating of the mixture at low heating rates favored the formation of binary phases in the solid state at medium temperatures. In this work, the T2 alloy with a fine-grained microstructure was obtained via a liquid–solid reaction when the mixture was heated fleetly to the temperatures above the silicon melting point at the rapid heating rate of 200 °C/min. The sintering temperature at 1500 °C for T2 synthesis is beneficial to enhance further densification, as well as to avoid abnormal grain growth at higher temperatures.

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► SPS is an effective method to synthesize T2 alloys.
► Extra 0.5 at% Si added to the powder mixture can offset volatilization loss of Si.
► Rapid heating rates suppress the appearance of second phases.
► The optimum sintering temperature for the production of T2 alloys is 1500 °C.