Surface morphologies of Zr52.5 Al10 Ni10 Cu15 Be12.5 bulk metallic glass after being rolled at both a temperature around T9 and near （ Tx - 50） K were investigated with a scanning electron microscopy. Macroscopic and microscopic observation results show that squamae, cracks, steps and wedges exist on the surface when the samples were rolled at temperatures around Ty. However, a smooth and fiat surface appears when the samples were rolled at temperatures near （ Tx - 50） K. These results indicate that the mode of deformation in the supercooled liquid region is a partially homogeneous flow at a temperature around T9, and a fully homogeneous one at temperatures near （ Tx - 50） K. According to the results, it is more feasible to roll the amorphous alloys at temperatures near （ Tx - 50） K to obtain parts with smooth and fiat surface.
Magnetic domain structure of hard magnetic Nd60Al10Fe20Co10 bulk metallic glass (BMG) has been studied by using magnetic force microscopy. In the magnetic force images it is shown that the exchange interaction type magnetic domains with a period of about 360 nm do exist in the BMG, which is believed to be associated with the appearance of hard-magnetic properties in this system. As the scale of the magnetic domain is much larger than the size of the short-range ordered atomic clusters existing in the BMG, it is believed that the large areas of magnetic contrast are actually a collection of a group of clusters aligned in parallel by strong exchange coupling interaction. After fully crystallization, the BMG exhibits paramagnetism. No obvious magnetic contrast is observed in the magnetic force images of fully crystallized samples, except for a small quantity of ferromagnetic crystalline phase with low coercivity and an average size of 900 nm.
Quasistatic and dynamic tensile behavior of Zr52.5Al10Ni10Cu15Be12.5 bulk amorphous alloy was investigated at the strain rates of 10-4-103 s-1 by using a Shimadzu AG-100KNA autograph and a pneumatic tensile impact tester. It was shown that the tensile fracture strength and the fracture morphology were sensitive to the strain rate. With the increase of the strain rate, the tensile fracture strength decreased and the fracture morphology changed from cleavage into quasi-cleavage, and then into a mixture of microvoid-coalescence dimples and quasi-cleavage veins.
Xueshan XIAO, Weihuo LI, Lei XIA, Shoushi FANG, Qin HUA and Yuanda DONGInstitute of Materials, Shanghai University, Shanghai 200072, China
