The effect of hot pressing time on the microstructure and properties of Laves phase NbCr₂alloys

The microstructure and properties were investigated on the Laves phase NbCr2alloys prepared through 20 h mechanical alloying of niobium and chromium powders and subsequent hot pressing at 1250 °C for different time. The results indicate that the Laves phase NbCr2alloy with homogeneous microstructure and fine grains and high relative density is obtained. With the increase of hot pressing time, the density, grain size and Vickers hardness increase, the fracture toughness, however, decreases gradually. The alloy fabricated by hot pressing at 1250 °C for 30 min has the best overall properties. Its average grain size reaches about 248 nm, the relative density is 97.8% and the fracture toughness at room temperature is more than 4.7 MPa m1/2. Compared with the Laves phase NbCr2alloy prepared by arc-melting, which has the fracture toughness of 1.2 MPa m1/2, the fracture toughness in this research is increased significantly.