Effects of Fe Addition on the Phase Transformation Internal Friction in Ni-Al-Based Alloys

The influences of chemical compositions on the internal friction of phase transformation were investigated for the quenched Ni-Al-based alloys. The internal friction measurements were completed using a low-frequency mechanical spectrum apparatus through forced vibration method. It was shown that the chemical compositions have the great influences on the internal friction of phase transition for the oil-cooled Ni-Al-based alloys. The peak-temperature of internal friction is lowered, and the peak-height is increased and the peak-width is narrowed when Fe content is elevated. The reducing of the peak-temperature is attributed to the increase of stability of γ phase due to the addition of Fe. The changes of the parameters of the peak are also related to the Aleq (equivalent Al) contents.

Design of the Leveling Mechanism of the Faceplate of Low Frequency Mechanical Spectrum Apparatus

A leveling mechanism of faceplate of low frequency mechanical spectrum apparatus is designed. The faceplate is kept horizontal and stable by the leveling mechanism when low frequency mechanical spectrum apparatus is installed or used. The present designed leveling mechanism can be used to adjust the faceplate up or down by turning the adjusting nut. In addition, the rubber pad with high damping capacity is installed on the leveling mechanism, producing vibration isolation effect.

High Temperature Mechanical Spectrum and Interstitial Oxygen in YBaCuFeO5+δ

Double perovskite oxide YBaCuFeO5+δ samples (labeled as “as-prepared”) were sintered by a solid-state reaction technique. Mechanical spectra of as-prepared sample were measured under vacuum condition from room temperature up to 720K by the reed vibration method. In the first heating run, two internal friction peaks were observed around 380 and 620K (labeled as P1 and P2, respectively) in YBaCuFeO5+δ. In the subsequent cooling run, both of them disappeared and a small step-like decrease of the internal friction around 500K was found. This step-like change was reproduced in the following thermal cycles. Thermogravimetric analysis (TGA) was also performed in order to monitor the oxygen content of the sample. It showed that the interstitial oxygen concentration decreased in the first heating run. The interstitial oxygen relaxation is suggested to be the origin of P1 peak. In dielectric measurements, a dielectric loss peak appeared around the temperature of the P2 internal friction peak and the peak temperature was independent on the measuring frequency. It is expected that P2 is associated with some kind of transitions of the interstitial oxygen. Further mechanical loss measurement of the annealed sample and scanning electron microscopy characterizing the as-prepared and annealed samples, provided more information on the interstitial oxygen in YBaCuFeO5+δ samples.

A Strain-Glass Transition Observed in Au7Cu5Al4 Ternary Alloys

Strain glass is a new type of glass state discovered recently in Ni-rich Ti-Ni ferroelastic alloys. It is formed by doping sufficient point defects such as solute atoms or alloying elements into a martensitic alloy to destroy the long range strain order generated by the diffusionless martensitic phase transformation. The strain glass was observed in an off-stoichiometric Heusler Au7Cu5Al4 alloy by the mechanical spectrum analysis. The martensitic transformation was experimentally confirmed following the occurrence of strain glass transition during the cooling. It is different from the model developed mainly in Ni-Ti based alloys among which the martensitic transformation was totally suppressed once the strain glass transition takes place. We conclude that newly observed strain glass in an off-stoichiometric Au7Cu5Al4 alloy belongs to one type of precursor phenomena.