Cavity of Al-Cu-Mg Alloy during Superplastic Deformation

2007 ◽  
Vol 551-552 ◽  
pp. 645-650
Author(s):  
Min Wang ◽  
Hong Zhen Guo ◽  
Y.J. Liu
Keyword(s):  
Strain Rate ◽  
Grain Boundaries ◽  
Superplastic Deformation ◽  
Room Temperature ◽  
Mg Alloy ◽  
Deformation Condition ◽  
Second Phase ◽  
Rate Condition ◽  
Second Phase Particles ◽  
Strain Rate Condition

According to the characteristic of appearing cavitation in the metals during superplastic deformation, the influence of strain rate on cavity evolvement, the influence of cavity on superplastic deformation capability, and the formation, development process of cavity were investigated for Al-Cu-Mg alloy (i.e. coarse–grained LY12). The results show that: ①The pore nucleation occurs not only at triangle grain boundaries, but also along nearby the second phase particles, and even within grains. The cavities at the triangle grain boundaries are present in V-shape, others near the second phase particles and within grains are present in O-shape. These cavities may result from disharmony slippage of grain boundaries. ②The tendency of cavity development decreases with increasing of strain-rate. In lower strain-rate condition, though Al-Cu-Mg alloy has better superplasticity, many big cavities in the specimen may reduce the room temperature properties of the alloy. In higher strain-rate condition, Al-Cu-Mg alloy has certain superplasticity and room temperature properties as well as few cavities forming. By analyzing, viscous layer on grain boundaries is very thin and grain sizes can be refined during their extruding and rotating each other in higher strain-rate superplastic deformation condition. ③Growth and coalescence of cavity are the main reason of the superplastic fracture of Al-Cu-Mg alloy. And small and a certain amount of cavities with dispersion and independence state are very useful to crystal boundary slippage.

A Constitutive Model for Strain-Induced Crystallization in Poly(ethylene terephthalate) (PET) during Finite Strain Load-Hold Simulations

2005 ◽  
Vol 128 (1) ◽  
pp. 28-33 ◽  
Author(s):  
Rebecca B. Dupaix ◽  
Dwarak Krishnan
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Complex Loading ◽  
Deformation Condition ◽  
Loading Conditions ◽  
Rate Condition ◽  
Strain Induced Crystallization ◽  
Strain Rate Condition ◽  
Poly Ethylene ◽  
Induced Crystallization

Recently, a hyperelastic-viscoplastic constitutive model was developed for PET and the noncrystallizing copolymer PETG (R. B. Dupaix, Ph.D. thesis, MIT, 2003). The materials were found to behave very similarly under monotonic loading conditions and the single constitutive model was able to capture both materials’ behavior. However, differences were observed upon unloading, and it is expected that additional differences would be observed under more complex loading conditions. Here their behavior is investigated under nonmonotonic loading conditions, specifically under load-hold conditions. The model of Dupaix and Boyce (R. B. Dupaix, Ph.D. thesis, MIT, 2003) is modified to include Ahzi’s upper-bound model for strain-induced crystallization [Ahzi et al., Mech. Mater., 35(12), pp. 1139–1148 (2003)]. The crystallization model is adapted to include criteria for the onset of strain-induced crystallization which depend on strain rate and level of deformation. The strain-rate condition prevents crystallization from beginning prior to the deformation process slowing significantly. The level-of-deformation condition delays crystallization until the material has deformed beyond a critical level. The combined model demonstrates differences in behavior between PET and PETG during complex loading situations, indicating its ability to capture the fundamental criteria for the onset of strain-induced crystallization.

The Room Temperature and Elevated Temperature Fracture Toughness Response of Alloy A-286

1978 ◽  
Vol 100 (2) ◽  
pp. 195-199 ◽  
Author(s):  
W. J. Mills
Keyword(s):  
Fracture Toughness ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Second Phase ◽  
Surface Micromorphology ◽  
Second Phase Particles ◽  
The Matrix ◽  
Temperature Fracture ◽  
Increasing Temperature ◽  
Base Superalloy

The elastic-plastic fracture toughness (JIc) response of precipitation strengthened Alloy A-286 has been evaluated by the multi-specimen R-curve technique at room temperature, 700 K (800°F) and 811 K (1000°F). The fracture toughness of this iron-base superalloy was found to decrease with increasing temperature. This phenomenon was attributed to a reduction in the materials’s strength and ductility at elevated temperatures. Electron fractographic examination revealed that the overall fracture surface micromorphology, a duplex dimple structure coupled with stringer troughs, was independent of test temperature. In addition, the fracture resistance of Alloy A-286 was found to be weakened by the presence of a nonuniform distribution of second phase particles throughout the matrix.

Continuous and Discontinuous Recrystallization of 6013 Aluminum Alloy

2013 ◽  
Vol 753 ◽  
pp. 221-224 ◽  
Author(s):  
Krzysztof Sztwiertnia ◽  
Magdalena Bieda ◽  
Anna Korneva
Keyword(s):  
Aluminum Alloy ◽  
Grain Boundaries ◽  
Second Phase ◽  
Sheet Plane ◽  
Temperature Range ◽  
Orientation Mapping ◽  
Second Phase Particles ◽  
The Matrix ◽  
Continuous Recrystallization

In situ orientation mapping using TEM and calorimetric measurements were carried out to investigate the annealing behavior of cold-rolled 6013 aluminum alloy. The recrystallization of the material can be considered to be a number of processes that correspond to two separate stored energy release peaks. In the temperature range of the peak 1, the deformation zones around the large second-phase particles acted as sites for particle-stimulated nucleation. In the matrix, at the same time, some elongation of grains occurred. The elongated matrix grains appeared because of the reduction of the dislocation density and the annihilation of some low-angle grain boundaries between chains of subgrains lying in layers parallel to the sheet plane. The matrix processes in this temperatures range can be considered forms of continuous recrystallization. The matrix high-angle grain boundaries started to migrate at the temperature range of the peak 2. They moved mostly in the direction normal to the sheet plane. Heating of the sample for an appropriate time at those temperatures resulted in the complete discontinuous recrystallization of the material. The recrystallized microstructure was dominated now by elongated grains, which were a few times thicker than those obtained by annealing at the temperatures of the peak 1.

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