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This work presents the effects of high energy milling with different Ni and Zr ratios on the amorphization of ternary Cu-Ni-Zr alloys (initially, Cu-43Ni-7Zr, Cu-12Ni-31Zr, Cu-33Ni-7Zr, and Cu-12Ni-23Zr; and later, Cu-23Ni-15Zr and Cu-11Ni-7Zr). Microstructure was determined using X-Ray diffraction and electron microscopy. Results were compared to thermodynamic models. In the ternary alloys under study, the lattice parameter of the Cu-Ni solid solution was generally correlated to the amounts of nickel incorporated into the Cu lattice. However, longer milling times reduced that lattice parameter and facilitated Zr insertion into the solid solution. For example, after 5 h of milling time, microstructural analysis showed the formation of a solid solution with cubic structure in Cu-43Ni-7Zr. This pattern is consistent with the presence of a lattice parameter between that of Cu and Ni (α−phase); in contrast, the Cu-33Ni-7Zr alloy showed an α-phase and another similar to Zr. Results suggest that, as the amount of nickel increases, the ability to form an amorphous phase decreases. Additionally, experimental and thermodynamic data showed a solid-solution formation stage, followed by an amorphous phase formation stage that occurred as milling time and Zr content increased. Fil: Martínez, Carola. Pontificia Universidad Católica de Valparaíso; Chile Fil: Aguilar, Claudio. Universidad Tecnica Federico Santa Maria; Chile Fil: Briones, Francisco. Pontificia Universidad Católica de Valparaíso; Chile Fil: Guzmán, Danny. Universidad de Atacama; Chile Fil: Zelaya, Maria Eugenia. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Troncoso, Loreto. Universidad Austral de Chile; Chile Fil: Rojas, Paula. Universidad Adolfo Ibañez; Chile

This work discusses the formation of Ti–30Nb–13Ta–xMn (x: 2, 4 and 6 wt%) solid solution by mechanical alloying using a shaker mill. A solid solution was formed after 15 h of milling and an amorphous phase was formed after 30 h of milling, according to X-ray diffraction results. Disappearance of strongest X-ray diffraction peaks of Nb, Ta and Mn indicated the formation of solid solution, while, X-ray diffraction patterns of powders milled for 30 h showed an amorphous hump with crystalline peaks in the angular range of 35–45° in 2θ. TEM image analysis showed the presence of nanocrystalline intermetallic compounds embedded in an amorphous matrix. Mn2Ti, MnTi and NbTi4 intermetallic compounds were detected and revealed crystallites with size ranging from 3 to 20 nm. The Gibbs free energy for the formation of solid solution and amorphous phase of three ternary systems (Ti–Nb–Ta, Ti–Nb–Mn and Ti–Ta–Mn) was calculated using extended Miedema's model. Experimental and thermodynamic data confirmed that solid solution was first formed in the alloy with 6wt% Mn followed by the formation of an amorphous phase as milling time increases. The presence of Mn promoted the formation of amorphous phase because the atomic radius difference between Mn with Ti, Nb and Ta.

Pure Ti and Ti-based alloys exhibit two equilibrium phases: at lower temperatures they have a hexagonal close packed (α-Ti) crystalline structure while at higher temperatures they possess a body-centered cubic (β-Ti) structure. However, in special conditions, they could exhibit a metastable face-centered cubic (γ-Ti) crystalline structure. This paper aims to investigate the influence of Sn amount and milling time on the formation of γ-Ti phase on the Ti-Ta based alloy. Four alloys with compositions Ti-13Ta-xSn (x: 3, 6, 9 and 12 at. %) were obtained by high energy milling. The alloys were analyzed by X-ray diffaction patterns, transmission and scanning electron microscopy. For the Ti-13Ta-3Sn alloy, the β-Ti phase is formed in greater quantity, ∼70% at 100 h. For the Ti-13Ta-6Sn and Ti-13Ta-9Sn alloys, the phase that is in greater quantity is γ-Ti, around 100% at 100h. The Ti-13Ta-6Sn alloy shows a greater tendency to form the γ-Ti phase, since the quantity is close to 100% at 50 h milling time. Thermodynamic calculations are comparable with experimental data. The calculations were made using the MAAT software based on Miedema’s model. The MAAT is a free software that can be download from www.rpm.usm.cl .

Phase evolution during mechanical alloying (MA) of elemental Mg and Cu powders and their subsequent heat treatment is studied. Elemental Mg and Cu powders in a 2:1 atomic ratio were mechanically alloyed in a SPEX 8000D mill using a 10:1 ball-to-powder ratio. X-ray diffraction (XRD) shows that the formation of the intermetallic Mg2Cu takes place between 3 and 4 h of milling, although traces of elemental Cu are still present after 10 h of milling. The thermal behavior of different powder mixtures was evaluated by differential scanning calorimetry (DSC). The combination of DSC, heat treatment and XRD has shown a sequence of phase transformations that results in the intermetallic Mg2Cu from an amorphous precursor. This amorphous phase is converted into Mg2Cu by heating at low temperature (407 K). Short MA times and the formation of the amorphous precursor, together with its subsequent transformation into Mg2Cu at low temperatures; represent an advantageous alternative route for its preparation.