Effect of silicon on the fracture toughness and oxidation behavior of hot pressed NbCr2 alloys

• Si partially occupies Cr site in Laves phase NbCr2 and partially forms Nb5Si3 phase.
• The addition of Si can harden and toughen as-HPed NbCr2 alloys.
• Fracture toughness of NbCr2–5 wt.% Si is 4 times higher than cast NbCr2 alloys.
• The toughening mechanism of Si on as-HPed NbCr2 alloys is firstly investigated.
• Silicon can enhance the oxidation resistance of NbCr2 alloys at 1373 K and 1473 K.

NbCr2 Laves phase alloyed with 0–7 wt.% Si was fabricated by mechanical alloying followed by hot pressing. The influence of silicon on the mechanical properties and oxidation behavior of NbCr2 were investigated. It was revealed that Si addition has a beneficial effect on the oxidation resistance and fracture toughness of NbCr2 alloy. The addition of Si partially occupies the Cr site in the Laves phase and partially forms the hard Nb5Si3 phase, which can yield an increase in the hardness of as-HPed NbCr2 alloys. When alloying with 5 wt.% silicon, the fracture toughness value of NbCr2 reaches the highest (6.45 MPa √m) which is about 13% more than that of unalloyed NbCr2 and is 4 times higher than that of cast materials (1.2 MPa √m). Addition of silicon also resulted in a substantial improvement in the oxidation resistance of the NbCr2 alloys exposed in air at 1373 K and 1473 K.