FLUCTUATION OF INTERNAL FRICTION IN METALLIC GLASSES

2011 ◽  
Vol 1300 ◽  
Author(s):  
Y. Miyauchi ◽  
R. Tamura ◽  
Y. Hiki
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Internal Friction ◽  
Metallic Glass ◽  
Transition Region ◽  
Frequency Spectrum ◽  
Metallic Glasses ◽  
Glass Transition Region ◽  
Characteristic Peak

AbstractInternal friction (IF) of a metallic glass Zr55Cu30Al10Ni5 has been measured near the glass transition temperature Tg (= 666 K). The measurement is performed by using DMA (TA Instrument) apparatus at a frequency of 0.01 Hz for a specimen stabilized by annealing. The specimen is kept at a constant temperature T, and the IF value Q-1 is measured as a function of time t. A fluctuation of Q-1 with time is seen, and the magnitude of the fluctuation, F(t), is derived from the Q-1-vs-t data. F(t) is Fourier transformed to the frequency spectrum F(f). Such experiment and analyses are carried out at various temperatures near Tg. A characteristic peak (f ~ 10-3 Hz) is found in the spectrum F(f) in the glass transition region.

scholarly journals Buckling and vibration analysis of shape memory laminated composite beams under axially heterogeneous in-plane loads in the glass transition temperature region

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Nilesh Tiwari ◽  
A. A. Shaikh
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Boundary Conditions ◽  
Shape Memory ◽  
Transition Region ◽  
Shape Memory Polymer ◽  
Shear Deformation Theory ◽  
Effect Of Temperature ◽  
Glass Transition Region

AbstractBuckling and vibration study of the shape memory polymer composites (SMPC) across the glass transition temperature under heterogeneous loading conditions are presented. Finite element analysis based on C° continuity equation through the higher order shear deformation theory (HSDT) is employed considering non linear Von Karman approach to estimate critical buckling and vibration for the temperature span from 273 to 373 K. Extensive numerical investigations are presented to understand the effect of temperature, boundary conditions, aspect ratio, fiber orientations, laminate stacking and modes of phenomenon on the buckling and vibration behavior of SMPC beam along with the validation and convergence study. Effect of thermal conditions, particularly in the glass transition region of the shape memory polymer, is considerable and presents cohesive relation between dynamic modulus properties with magnitude of critical buckling and vibration. Moreover, it has also been inferred that type of axial loading condition along with the corresponding boundary conditions significantly affect the buckling and vibration load across the glass transition region.

scholarly journals The Dynamic Constants of Unidirectional Fibrous Composites at the Glass Transition Region as Obtained from the Interphase Concept

2018 ◽  
Author(s):  
Emilio Sideridis ◽  
John Venetis
Keyword(s):  
Composite Material ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Transition Region ◽  
Loss Factor ◽  
Intermediate Phase ◽  
Mechanical Analysis ◽  
Fibrous Composites ◽  
Glass Transition Region

Dynamic mechanical analysis (DMA) is a versatile technique that complements the information given by the more traditional thermal analysis techniques such as differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and thermal mechanical analysis (TMA). Dynamic constants such as storage modulus, loss modulus, and loss factor are temperature dependent and provide information about interfacial bonding between reinforced fibre and polymer matrix of composite material. To study the above mentioned properties at the glass transition region, for unidirectional fibrous composites reinforced with continuous fibers a reliable model was applied. In particular, the composite material was considered as composed of three phases with the intermediate phase between matrix and fibres, the interphase, to have variable properties depending on those of main phases and the mode of preparation of the overall material. The glass transition temperature is defined as the point at which the specific volume versus temperature curve changes abruptly slope marking the region between rubbery polymer and glassy polymer nature. Hence, the behaviour of unidirectional fibrous composites was investigated at this region. Examination of the glass transition temperature, which constitutes an upper limit for the structurally important glassy region through the loss factor, was performed by its consideration as a combination of glass transition temperature of matrix and interphase.

Modification of the Mechanical Behavior in the Glass Transition Region of Poly(lactic acid) (PLA) through Catalyzed Reactive Extrusion with Poly(carbonate) (PC)

2015 ◽  
Vol 1119 ◽  
pp. 292-295
Author(s):  
Vu Thanh Phuong ◽  
Maria Beatrice Coltelli ◽  
Irene Anguillesi ◽  
Patrizia Cinelli ◽  
Andrea Lazzeri
Keyword(s):  
Thermal Stability ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Transition Region ◽  
Reactive Extrusion ◽  
Maximum Temperature ◽  
Glass Transition Region ◽  
The One ◽  
Poly Carbonate

In order to improve the thermal stability of PLA based materials it was followed the strategy of blending it with a polymer having a higher glass transition temperature such as poly (carbonate) of bisphenol A (PC) . PLA/PC blends with different compositions were by melt extrusion produced also in the presence of an interchange reaction catalyst, tetrabutylammonium tetraphenylborate (TBATPB) and triacetin. The dynamical mechanical thermal characterization showed an interesting change of the storage modulus behavior in the PLA glass transition region, evident exclusively in the catalyzed blends. In particular, a new peak in the Tan δ trend at a temperature in between the one of PLA and the one of PC was observed only in the blends obtained in the presence of triacetin and TBATPB. The height and maximum temperature of the peak was different after the annealing of samples at 80°C. The data showed an interesting improvement of thermal stability above the PLA glass transition, this was explained keeping into account the formation of PLA-PC copolymer during the reactive extrusion. Furthermore, the glass transition temperature of the copolymer as a function of composition was studied and the obtained trend was discussed by comparing with literature models developed for copolymers.

The evolution of structural and elastic properties of a Zr-based metallic glass upon annealing below glass transition temperature

2019 ◽  
Vol 33 (01n03) ◽  
pp. 1940053 ◽  
Author(s):  
F. Zhang ◽  
X. C. Wang ◽  
P. Deng ◽  
X. M. Qin ◽  
J. Tan
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Elastic Properties ◽  
Metallic Glasses ◽  
Shear Velocity ◽  
Testing Device ◽  
Free Volume Theory

Bulk metallic glasses are often used well below their glass transition temperatures, Tg, because of their change in the physical properties of the material through its glass transition, which is not considered a phase transition; rather it is a phenomenon extending over a range of temperature and is defined by a viscosity threshold of 101 2 Pa ⋅ s. In this work, a Zr-based metallic glass upon annealing below glass transition temperature (Tg–30 K) was quasi-in-situ investigated. The structural and elastic properties were observed carefully by utilizing an in-house designed density testing device and an ultrasonic testing device. We found out that the density, the shear velocity, the longitudinal wave velocity, and the elastic modulus increased through annealing at 719 K for 300, 900 and 1500 s. A possible explanation was presented based on the free volume theory and it was found that the relaxation kinetics in this study obeyed the Kohlraush–Williams–Watts (KWW) relaxation function with [Formula: see text] = 0.420 [Formula: see text] 1 implying that the relaxation mechanisms were multiple ones.

scholarly journals Effects of Annealing on Enthalpy Recovery and Nanomechanical Behaviors of a La-Based Bulk Metallic Glass

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 579
Author(s):  
Ting Shi ◽  
Lanping Huang ◽  
Song Li
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Structural Relaxation ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
Nanoindentation Measurement

Structural relaxation and nanomechanical behaviors of La65Al14Ni5Co5Cu9.2Ag1.8 bulk metallic glass (BMG) with a low glass transition temperature during annealing have been investigated by calorimetry and nanoindentation measurement. The enthalpy release of this metallic glass is deduced by annealing near glass transition. When annealed below glass transition temperature for 5 min, the recovered enthalpy increases with annealing temperature and reaches the maximum value at 403 K. After annealed in supercooled liquid region, the recovered enthalpy obviously decreases. For a given annealing at 393 K, the relaxation behaviors of La-based BMG can be well described by the Kohlrausch-Williams-Watts (KWW) function. The hardness, Young’s modulus, and serrated flow are sensitive to structural relaxation of this metallic glass, which can be well explained by the theory of solid-like region and liquid-like region. The decrease of ductility and the enhancement of homogeneity can be ascribed to the transformation from liquid-like region into solid-like region and the reduction of the shear transition zone (STZ).

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