Glass Formation of Null-Matrix Cu-Hf-(Zr, Ti) Alloys
An approach following the null-matrix, Ti/Zr ratio of 2.08, for neutron diffraction was used to calculate the glass formation in Cu-Ti-(Hf,Zr) alloys. The Cu55Zr14.6Ti30.4, Cu61.48Hf18.52Zr6.48Ti13.52, Cu58.1Hf16.9Zr8.1Ti16.9 and Cu52.46Hf14.2Zr10.8Ti22.54 compositions (at. %), were calculated and prepared by argon arc melting. Copper die suction casting was employed to produce conical shaped samples with diameters decreasing from 8 mm to 1 mm. X-ray diffraction and Neutron Diffraction were used to characterize the alloys with the aim of obtaining the critical glassy diameter, dc, of the alloys. The results showed the composition with the biggest dc was the Cu61.48Hf18.52Zr6.48Ti13.52 alloy, with dc = 6 mm. Thermal parameters were obtained by differential scanning calorimetry and the maximum values for glass transition temperature, Tg, (747 K), crystallization temperature, Tx, (772 K), solidus temperature, Tm, (1152 K) and liquidus temperature, Tl, (1230 K) corresponded to the Cu61.48Hf18.52Zr6.48Ti13.52 composition. The results also showed that the parameters obtained from thermal analysis did not correlate with the GFA obtained. However, a good correlation of GFA and dc was found by means of the topological model, where the highest % packing efficiency (53.57 %) was found for the Cu61.48Hf18.52Zr6.48Ti13.52 alloy, which also showed the highest dc value with 6 mm.