Effect of mechanical alloying on microstructure, mechanical properties and oxidation behavior of hot pressed nanocrystalline Cr–33 Nb alloys

Cr–33 at.% Nb alloys were prepared by mechanical alloying and hot pressing (HP). The influences of mechanical alloying on microstructure, mechanical properties and oxidation behaviors of the hot pressed specimens were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron transmission microscopy. The results indicate that nanocrystallite NbCr2 Laves phase is obtained. With increasing the milling time from 0 to 100 h, the relative density and microhardness of the hot pressed compacts increase and the grain size decreases gradually. The hot pressed alloy made with the as-MAed powders for 20 h has the best oxidation resistance. The fracture toughness values measured using the indentation method were observed to be 3.7–5.7 MPa√m, which are two to four times higher than that of cast materials (1.2 MPa√m).