A mechanical spectroscopy study of Cu-Zr-Al bulk metallic glasses, was performed with two types of equipment: a Kê-type inverted torsion pendulum and an acoustic elastometer, working in the frequency ranges of Hz and kHz, respectively, with a heating rate of 1 K/min. The analysis of the anelastic relaxation shows similar spectra for both types of equipment resulting in internal friction patterns that vary with temperature and are not reproducible at each thermal cycle. The normalized of the square of the frequency changes from the first to later measurement cycles. These results indicate that the specimens of Cu-Zr-Al alloys were changing by mechanical relaxation, owing to the motion of atoms or clusters in the glassy state and possible "defects" produced during the processing of alloys.

Dynamical Elastic Moduli of the Ti-13Nb-13Zr biomaterial alloy were obtained using the mechanical spectroscopy technique. The sample with heat treatment at 1170K for 30 minutes and water quenched with subsequent aging treatment at 670 K for 3 hours (TNZ + WQ + 670 K/3 h), was characterized through decay of free oscillations of the sample in the flexural vibration mode. The spectra of anelastic relaxation (internal friction and frequency) in the temperature range from 300 K to 625 K not revealed the presence of relaxation process. As shown in the literature, the hcp structure usually does not exhibit any relaxation due to the symmetry of the sites in the crystalline lattice, but if there is some relaxation, this only occurs in special cases such as low concentration of zirconium or saturation of the stoichiometric ratio of oxygen for zirconium. Dynamical elastic modulus obtained for TNZ + WQ + 670 K/3 h alloy was 87 GPa at room temperature, which is higher than the value for Ti-13Nb-13Zr alloy (64 GPa) of the literature. This increment may be related to the change of the proportion of α and β phases. Besides that, the presence of precipitates in the alloy after aging treatment hardens the material and reduces its ductility.

En este trabajo se determinaron las características de un material arcilloso de la región de Guapi, Cauca, Colombia. Se estableció, además, una metodología para definir las condiciones más adecuadas para conformar piezas cerámicas. Para ello se analizó la composición química, características estructurales y comportamiento térmico de la materia prima de interés, utilizando análisis de fluorescencia de rayos X (FRX), difracción de rayos X (DRX) y análisis termogravimétrico (ATD/TG), respectivamente. Posteriormente, se estudiaron las diferentes etapas del procesamiento cerámico poniendo atención a la dosificación de la pasta cerámica, el prensado de las piezas, su secado y sinterización, controlando variables como presión de conformado, pérdida de peso, tiempo de secado, densidad en verde y temperatura de sinterización, entre otras. Para lograr un adecuado secado de las muestras fue necesario mantenerlas en un ambiente con humedad controlada durante ~7 días. Independiente de la composición de las pastas, para obtener piezas densificadas, fue necesario sinterizar a temperaturas mayores a 1.000 °C considerando que a 950 °C se presentó desdensificación de la muestra ocasionada, posiblemente, por un fenómeno de tipo "Ostwald ripening" en la porosidad.

In this work the characteristics of clay from the region of Guapi, Cauca, Colombia were determined. Also, a methodology was established to defi ne the conditions to conform ceramic pieces. Chemical structure, characteristic composition and thermal behavior of raw material were determined using X-ray fl uorescence, (FRX), X- ray diffraction (DRX) and thermal gravimetric analysis (ATD/TG), respectively. Different stages of the ceramic processing were studied paying attention to dosage of the ceramic pastes, pressing of the pieces, drying and sintering. Variables controlled were shaping pressure, lost of weight, time of drying, density in green and sintering temperature, among others. To achieve an appropriate drying it was necessary to maintain the samples in a controlled humidity atmosphere during about 7 days. Independent of the composition of the pastes, sintering above 1000 °C was necessary to obtain high density samples considering that at 950 °C des-density of samples was observed probably due to "Ostwald ripening" type phenomenon.