Thermoplastic deformation behavior of a Fe-based bulk metallic glass within the supercooled liquid region

Abstract

Fe41Cr15Co7Mo14C12B9Y2 (Fe-B9) bulk metallic glass (BMG) rods with high glass forming ability and large supercooled liquid (SCL) region were fabricated by arc melting and suction casting. The amorphous state of these Fe-B9 BMG rods was ascertained by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The thermoplastic deformation behavior of these BMG rods was studied by using the hot compression test at different temperatures (873 K, 883 K, 893 K, and 903 K in the SCL region) and strain rates (1 × 10−3–5 × 10−2 s−1). The results of the hot compression test reveal that the flow stress of Fe-B9 BMG reduces systematically with increasing temperature and decreasing strain rate. Strain sensitivity exponent (m) values of the Fe-B9 BMG were calculated to be about 0.36–0.59 in the SCL region, indicating that Fe-B9 BMG possesses superplasticity. Overall, the optimum working conditions of thermoplastic forming for Fe-B9 BMG can be achieved by compressively deforming the sample with a constant strain rate of 2.5 × 10−3 s−1 at a temperature from 873 to 883 K. Keywords: Metallic glasses, Viscous flow, Superplasticity, Mechanical properties, Casting