Papers by Author: L. Lu

Abstract: This paper explores the wear characteristics of nanocrystalline Mg-5%Al-5%Nd, synthesized by mechanical alloying. Pin-on-disc unlubricated sliding wear tests were conducted against a hardened tool-steel counterface under loads of 10 and 30 N, and within a velocity range of 0.2-5.0 m/s. Despite its appreciably superior mechanical properties, the nanostructured alloy did not exhibit the expected improvement in wear resistance when compared to its conventional microngrain- sized counterpart; in fact, the former performed worse when testing conditions became more severe. Scanning electron microscopy (SEM) suggested that extensive delamination in the nanocrystalline alloy was the primary reason for its high wear rates. This wear mechanism was promoted by the presence of MgxNd dispersiods, which were found only within the nanocrystalline material. These compounds likely resulted from the long duration (20 hrs) of ball-milling, which was the mechanical alloying technique employed to reduce the grain size of the final alloy.

Abstract: Formation of partial nanocrystal and amorphous tungsten alloys was synthesized via crystallization of a completely amorphized tungsten alloy synthesized by mechanical alloying. Structural characterization shows formation of amorphous structure from mechanical alloying of a mixture of elemental tungsten and iron powders after about 150 hours. Partial nanocrystalline phases within the amorphous matrix were formed through annealing the amorphous tungsten alloy at 1075°C.