Chapters authored
Structure and Mechanical Behaviour of Cu‐Zr‐Ni‐Al Amorphous Alloys Produced by Rapid Solidification
The amorphous ribbons of Cu50Zr40Ni5Al5 alloy were manufactured by rapid solidification. The ribbons were investigated by X‐ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM‐EDX) and differential scanning calorimetry (DSC). The activation energy of the crystallisation in amorphous alloys was determined by Kissenger technique. The mechanical properties of the ribbons were characterized using Vickers microhardness (HV) tester. According to the XRD and SEM results, the Cu50Zr40Ni5Al5 alloys have a fully amorphous structure. The EDX analysis of the ribbons showed that compositional homogeneity of the Cu50Zr40Ni5Al5 alloy was fairly high. From the DSC curves of the amorphous ribbons, it was determined that glass transition temperature (Tg) is around 440–442°C and super‐cooled liquid region (ΔTx = Tx - Tx) before crystallisation is around 61–64°C. The microhardness of the as‐quenched ribbons was measured about 550 HV. However, this microhardness value decreased with increasing annealing temperature and it was calculated about 465 HV after annealing temperature of 800°C.
Part of the book: Metallic Glasses
Phase Identification and Size Evaluation of Mechanically Alloyed Cu-Mg-Ni Powders
Ternary mixture of Cu, Mg, and Ni with the nominal composition of nanocrystalline Cu50Mg25Ni25 (in at.%) was milled for 25 hours. Analysis of an X‐ray diffraction pattern (XRD) and transmission electron microscopy (TEM) was used to characterize the chemical phases and microstructure of the final product, which is shown to consist of ternary alloy of Cu‐Mg‐Ni with FCC structure along with small amounts of FCC MgO and Mg0.85Cu0.15. The good agreement between the size values obtained by XRD and TEM is attributed to the formation of defect‐free grains with no substructure during ball milling. Dynamic recrystallization may be a possible mechanism for the emergence of such small grains (<20 nm). The particle size distribution and morphological changes of Cu–Mg–Ni powders were also analyzed by scanning electron microscopy (SEM). According to the SEM results, the particle size of the powders decreased with increasing milling time. Lattice parameter of the Cu‐Mg‐Ni ternary FCC alloy formed during mechanical alloying increased with increase in milling time from 3.61 to 3.65 Å after 20 hours milling.
Part of the book: Nanostructured Materials