Influence of Low Oxygen Contents and Alloy Refinement on the Glass Forming Ability of Zr_(52.5)Cu_(17.9)Ni_(14.6)Al_(10)Ti_5

摘要

The effect of additions of C, Si, Ca, Sc and La at levels of 0.1, 0.3 and 1.0 atomic percent on the glass forming ability of the alloy Zr_(52.5)Cu_(17.9)Ni_(14.6)Al_(10)Ti_5 has been investigated by means of metallography, X-ray diffraction and oxygen analysis using wedge shaped castings. In the original alloy, a very marked influence of oxygen on the glass forming ability is observed even at low concentrations. Low amounts of additional elements were found to influence the glass forming ability significantly. Adding Sc to alloys containing 100-120 ppm oxygen increases the glass forming ability from 4.5 to 10 mm in terms at amorphous ingot thickness. These results were confirmed with additional samples, and best glass forming ability was found with additions of 0.03 percent to 0.06 percent Sc. The maximum amorphous thickness in the wedges as measured by metallography correlates within an accuracy of about 1 mm with that measured by X-ray diffraction over a wide range of modified alloys. A possible mechanism for the enhancement of glass formation through these dopants, and reasons for their effectiveness over only a limited concentration range, are discussed using results from differential scanning calorimetry and differential thermal analysis on a series of samples with different Sc concentrations.