On Glass Forming Ability of Bulk Metallic Glasses by Relating the Internal Friction Peak Value

The internal friction (IF) behaviors of a series of LaCe-, Zr-, and La-based bulk metallic glasses (BMGs) were studied by a computer-controlled, conventional inverted torsion pendulum. The results indicate that with an increasing temperature, the IF also increases gradually in the supercooled liquid region, followed by a decrease caused by crystallization. BMGs with a good glass forming ability (GFA) usually possess a high IF peak value for an alloy system with the same constituent elements. Furthermore, the magnitude of the IF value (Qi−1) of the inflection point is an efficient criterion of GFA. The Qi−1 value is a valid criterion under the conditions of identical constituent elements and different element contents. However, Qi−1 and GFA have no relationship among different alloy systems.

Development of the Snoek Anelastic Relaxation Correlated with Oxygen in β-Ti Alloys

The β-Ti alloys exhibit excellent shape memory effect and superelastic properties. The interstitial atoms in the alloys have important effect on their physical and mechanical properties. For the interstitial atoms, the internal friction technique can be used to detect their distributions and status in the alloys. The anelastic relaxation in β-Ti alloys is discussed in this paper. β-Ti alloys possesses bcc (body center body) structure. The oxygen (O) atoms in in the alloys is difficult to be removed. The O atoms located at the octahedral sites in the alloys will produce relaxation under cycle stress. In addition, the interaction between the interstitial atoms and substitute atoms, e.g., Nb-O,Ti-O can also produce relaxation. Therefore, the observed relaxational internal friction peak during the measuring of internal friction is widened. The widened multiple relaxation peak can be revolved into Debye,s elemental peaks in Ti-based alloys. The relaxation peak is associated with oxygen movements in lattices under the application of cycle stress and the interactions of oxygen-substitute atoms in metastable β phase (βM) phase for the water-cooled specimens and in the stable β (βS) phase for the as-sintered specimens. The damping peak height is not only associated with the interstitial oxygen, but also the stability and number of βM in the alloys.

High Temperature Internal Friction Relaxations in Cold-Rolled Titanium

The high temperature relaxation in cold-rolled Ti (CR-Ti) and commercial pure Ti (CP-Ti) has been investigated using internal friction apparatus operating in forced oscillations from room temperature to 650°C. It is shown that there is an internal friction peak at around 510°C for the CR-Ti and there is no 510°C internal friction peak in the CP-Ti. The internal friction peak shows typical features of phase transformation in the CR-Ti. It is tentatively suggested that this peak is due to the ordering of disordered lattices resulted from cold-rolling. The high temperature background damping (HTBD) in the CP-Ti is much lower than that in the CR-Ti. It is concluded that the HTBD is related to the microstructure observed inside the grains and does not dependent on grain size.

Microstructure and Damping Capacity of AlNp/Mg-Al Composites with Different Particle Contents

The AlN particles reinforced magnesium-aluminum matrix composites were fabricated by powder metallurgy and the damping mechanism was discussed. The results showed that the best damping capacity of composite reached with the addition of 6wt% AlN reinforcement, while the AlN particles were uniformly dispersed in the matrix. The damping capacity of composites decreases with the increasing of the reinforcement content and the experimental frequency. The internal friction peak related to dislocation appearance in the temperature ranges of 100-150°C. In addition, another internal friction peak of composites between 200 and 250°C arose, which was related to interface sliding.

Low-Frequency Mechanical Spectroscopy of Lanthanum Cobaltite Based Mixed Conducting Oxides

The low-frequency mechanical spectra of lanthanum cobaltite based mixed conducting oxides have been measured using a computer-controlled inverted torsion pendulum. The results indicate that the internal friction spectra and shear modulus depend on the Sr doping contents (x). For undoped samples, no internal friction peak is observed. However, for La0.8Sr0.2CoO3‒δ, three internal friction peaks (P2, P3 and P4) are observed. In addition to these peaks, two more peaks (P0 and P1) are observed in La0.6Sr0.4CoO3‒δ. The P0 and P1 peaks show characteristics of a phase transition, while the P2, P3 and P4 peaks are of relaxation-type. Our analysis suggests that the P0 peak is due to a phase separation and the P1 peak is related to the ferromagnetic–paramagnetic phase transition. The P2, P3 and P4 peaks are associated with the motion of domain walls. The formation of this kind of domain structure is a consequence of a transformation from the paraelastic cubic phase to the ferroelastic rhombohedral phase. With partial substitution of Fe for Co, only one peak is observed, which is discussed as a result of different microstructure.

Study on the Synthesis and Properties of MAH-POE/LMW-EP/PP/CaCO3 Quadruple Composites

This paper adopted the mixing modification to prepare MAH-POE/ LMW-EP/PP/CaCO3 thermoplastic composites, probed into the structure of composites, the system compared the modification made by composites and the single system of the rheological property, the influence law of flow rate, mechanical properties, dynamic mechanical thermal analysis (DMTA) and the network structure of the composite material etc. The results showed that the elastomer was preferably dispersed in the PP, the two phases have a strong interaction force, When the content reaches 20%, the tensile strength decreased by 7.37%, the elongation at break increased by 410.1%, the impact strength reached 546.3J.m2, there has been broad and strong low internal friction peak tanδ2 peak, and with the increase of elastomer content, liquidity blends decreases, MFR decreases. In short, quadruple composites have optimum overall performance. Polypropylene (PP) is a source of abundant, excellent mechanical properties, good electrical insulation, and resistance to stress cracking and has good overall performance excellent chemical stability thermoplastics. Widely used in medical equipment, auto parts , building materials, home office supplies, as well as a large number of transport and packaging materials [1-3] . However, due to the strong ability of PP crystallization, resulting PP mold shrinkage, impact toughness is poor [4-5] , in order to solve this problem , the current modification methods often used are: copolymerization and blending modification , and blending is the most simple and effective toughening PP method . The main focus ① blended with a modified rubber or thermoplastic elastomer blends toughening ; ② Toughening with other organic polymers ; ③ rigid inorganic particle toughening ; ④ elastomer / toughening common inorganic particles [6-10] . POE because both thermoplastic plastics , but also the crosslinkable rubber , which has a small cohesive energy , high shear sensitivity , and good compatibility with PP machining , toughening modification of PP the effect is significant and widespread attention , but the larger POE elastomer modified PP viscosity , processing performance be affected [11-13] . In this paper, LMW-EP and MAH-POE-modified PP, while adding CaCO3 prepared by a four-element composite elastomer material, by contrast, explores the compatibility of the quaternary blends, processing fluidity and mechanical properties

Internal Friction of Li7La3Zr2O12 Based Lithium Ionic Conductors

The diffusion mechanisms of lithium ions in tetragonal phase as well as in Al and Nb stabilized cubic Li7La3Zr2O12 compounds were investigated by low-frequency internal friction technique. In the cubic Li7La3Zr2O12 phase, a remarkable relaxation-type internal friction peak PC with a peak height up to 0.12 was observed in the temperature range from 15°C to 60°C. In the tetragonal phase however, the height of the PT peak dropped to 0.01. The obvious difference of the relaxation strength between the cubic and tetragonal phases is due to the different distribution of lithium ions in lattice, ordered in the tetragonal phase and disordered in the cubic phase. Based on the crystalline structure of the cubic garnet-type Li7La3Zr2O12 compound, it is suggested that the high internal friction peak in the cubic phase may be attributed to two diffusion processes of lithium ions: 96h↔96h and 96h↔24d.