Phase constitution and glass formation of U-Pd-Ni-Si alloys

Abstract

In order to explore U-based alloys having high glass forming ability (GFA), a series of U-Pd-Ni-Si alloys with 60% U were designed on the basis of the eutectic features of U-Ni and U-Pd base systems together with the Si addition. Their ingots and ribbons were prepared by arc-melting and melt-spinning methods and further examined to reveal the phase constitution and amorphization behavior mainly by X-ray diffraction and differential scanning calorimetry. The results show that these alloys can form U6Ni type (NU) and/or α-U type (AU) phases under a quasi-equilibrium or equilibrium condition and amorphous phase, completely for most of them, under a non-equilibrium condition. A possibly Pd-based glassy phase seemed to unexpectedly arise in two Pd-rich alloy ingots, which would be the first observation of glass formation in U-based alloys solidified at low cooling rates. Within all the U-Pd-Ni-Si alloys, the ones with a big Ni/Pd ratio, thus tending to get NU phase, can achieve substantially higher GFA than the others with small Ni/Pd and a tendency to AU phase. Especially, U60Pd7.5Ni25Si7.5 and U60Pd5Ni25Si10 displayed firstly the reduced glass transition temperature Tg/TL of > 0.6 and a wide supercooled liquid region of ~100 K, exhibiting a GFA level superior to the whole reported U-based metallic glasses (MGs) and comparable to some traditional bulk MGs. All the yields reflect that Ni plays stronger roles in both compounding with U and the glass formation than Pd and Si in these alloys, and also offer guidance for creating novel U-based metallic materials including better MGs.