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.本研究采用遵循零矩阵（null-matrix）且Ti/Zr比为2.08的中子衍射方法，对Cu-Ti-(Hf,Zr)合金的玻璃形成能力进行计算。所研究的Cu55Zr14.6Ti30.4、Cu61.48Hf18.52Zr6.48Ti13.52、Cu58.1Hf16.9Zr8.1Ti16.9及Cu52.46Hf14.2Zr10.8Ti22.54四种原子百分比（at.%）成分的合金，均通过氩弧熔炼完成制备与相关计算。采用铜模吸铸法制备了直径从8 mm递减至1 mm的锥形试样。借助X射线衍射（X-ray diffraction）与中子衍射（neutron diffraction）对合金进行表征，以获取合金的临界玻璃态直径dc。结果显示，Cu61.48Hf18.52Zr6.48Ti13.52合金的临界玻璃态直径dc最大，为6 mm。通过差示扫描量热法（Differential Scanning Calorimetry, DSC）获取热分析参数，其中玻璃转变温度（glass transition temperature, Tg）、结晶温度（crystallization temperature, Tx）、固相线温度（solidus temperature, Tm）与液相线温度（liquidus temperature, Tl）的最大值分别为747 K、772 K、1152 K和1230 K，均对应Cu61.48Hf18.52Zr6.48Ti13.52合金成分。研究还发现，热分析所得参数与测得的玻璃形成能力（glass formation ability, GFA）并无关联。不过通过拓扑模型（topological model）分析发现，玻璃形成能力与临界玻璃态直径dc之间存在良好相关性；其中Cu61.48Hf18.52Zr6.48Ti13.52合金的堆积效率（packing efficiency）最高，达53.57%，其临界玻璃态直径dc同样达到最大值6 mm。