SYNTHESIS AND MICROSTRUCTURAL EVOLUTION OF AL-NI-FE-GD METALLIC-GLASSBY MECHANICAL ALLOYING

Amorphous Al80Ni8Fe4Gds quaternary powders are successfully produced u sing the mechanical alloying (MA) technique, suggesting that powder me tallurgy techniques may be used in the manufacture of aluminum-transit ion metal-rare earth metallic glasses as high-strength, low-density en gineering materials. Detailed investigations into the microstructural evolution of the amorphous phase from elemental powders are presented, employing scanning and transmission electron microscopy, as well as, analytical techniques. The results show that it is possible to amorphi ze higher-order systems by MA, and the observations of the amorphizati on reaction support the interdiffusion-based model developed from stud ies of simple binary systems, with certain adjustments. The resulting amorphous powder demonstrates good thermal stability, and consolidated amorphous bulk material up to 93% dense are easily produced. Mechanic al properties of the amorphous phase are evaluated, including measurem ent of Vickers hardness and fracture toughness. K(c) is found to lie i n the range of 1-5 MPa/m1/2, identifying the produced powder as the br ittle-type amorphous phase seen in earlier work. Dispersed ductile nan ocrystals improve the fracture toughness at the expense of Vickers har dness.