Narrow Results

We have produced powders of nanostructured and amorphous alloys as well as bulk amorphous alloys with composition Zr₆₄Cu₁₈Ni₁₀Al₈ by mechanical alloying and by quenching arc melted melts in water cooled cooper dies, respectively. The alloys were investigated by X-ray diffraction as well as by thermal analysis in order to determine the structure and thermal properties. The mechanical alloyed amorphous powders and bulk amorphous cylinders show the same thermal and X-ray characteristics. For the amorphous powders, we find that the glass transition temperature T_g is 657 K and the crystallization temperature T_x is 752 K. For bulk amorphous alloys with the same composition prepard by arc melting and liquid quenching T_gis 655 K and the T_x is 725 K. Moreover for the bulk amorphous alloys the supercooled liquid region Δ T_xg is 70 K, the reduced glass transition temperature t_g is 0.557, the Lu–Liu parameter γ which represents the glass forming ability for bulk metallic glasses is 0.396 and experimentally the critical cooling rate R_c takes the value 7 K s^-1.

Nd₂Fe${}_{13.6}$Zr${}_{0.4}$B hard magnetic material were prepared using arc-melting technique on a water-cooled copper hearth kept under argon gas atmosphere. The prepared samples, Nd₂Fe${}_{13.6}$Zr${}_{0.4}$B ingot and ribbon are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) for crystal structure determination and morphological studies, respectively. The magnetic properties of the samples have been explored using vibrating sample magnetometer (VSM).

The lattice constants slightly increased due to the difference in the ionic radii of Fe and that of Zr. The bulk density decreased due to smaller molar weight and low density of Zr as compared to that of Fe. Ingot sample shows almost single crystalline phase with larger crystallite sizes whereas ribbon sample shows a mixture of amorphous and crystalline phases with smaller crystallite sizes. The crystallinity of the material was highly affected with high thermal treatments. Magnetic measurements show noticeable variation in magnetic behavior with the change in crystallite size. The sample prepared in ingot type shows soft while ribbon shows hard magnetic behavior.