DSC Analysis of LT-3 Aluminum Alloy Vacuum Brazing

LT-3 aluminum alloy is a kind of two-side cladding aluminum special used in vacuum brazing. Differential Scanning Calorimeter （DSC） was used to measure the exothermic and endothermic reaction during the brazing process that the cortex metal and the base metal are melted and re-crystal. The analysis results inidicate that eutectic reaction is the main reaction in the melted cortex metal crystallization process. But the main reaction in the melted base metal crystallization process is the reaction that α-A1 segregated out. According to the experimental details, the critical work of nucleation is 3.82×10-17J, the critical radius of nucleation is 8.69×10-10 m, the volume of critical crystal nucleus is 2.75×10-27 m3 and the per unit cell in critical crystal nucleus is 43.

Characterization and kinetic modeling of secondary phases in squeeze cast Al alloy A380 by DSC thermal analysis

Thermal analyses on squeeze cast aluminum alloy A380(SC A380) solidified under 90MPa were carried out to study the microstructure development of the alloy, in which a differential scanning calorimeter(DSC) was employed. During the DSC runs, heating and cooling rates of 1, 3, 10, and 20 °C·min^(-1) were applied to investigate the heating and cooling effects on dissolution of secondary eutectic phases and microstructure evolution. Various reactions corresponding to troughs and peaks of the DSC curves were identified as corresponding to phase transformations taking place during dissolution or precipitation suggested by the principles of thermodynamics and kinetics. The comparison of the identified characteristic temperatures in the measured heating and cooling curves are generally in good agreement with the computed equilibrium temperatures. The microstructure analyses by scanning electron microscopy(SEM) with energy dispersive X-ray spectroscopy(EDS) indicate that the distribution and morphology of secondary phases present in the microstructure of the annealed sample are similar to the as-cast A380, i.e., strip β(Si), buck bone like or dot distributed θ(Al_2Cu), β(Al_5Fe Si) and Al_(15)(FeMn)_3Si_2. Two kinetic methods are employed to calculate the activation energies of the three common troughs and three common peaks in DSC curves of SC A380. The activation energies of the identified reaction θ_(CuAl_2) = α(Al)+β(Si) is 188.7 and 187.1 k J?mol^(-1) when the activation energies of reaction α(Al)+β(Si)→θCu Al_2 is^(-1)22.7 and^(-1)21.8 k J?mol^(-1), by the Kissinger and Starink methods, respectively.

Superplastidty of a SiC particulate-reinforced 6A02A1 matrix composite

The superplastic characteristics of a 15% (volume fraction) SiCp (14μm)/6A02Al composite, fabricated by stirring casting and cold-rolling after extrusion with a lowextrusion ratio of 10:1 and hot-rolling, were investigated. The composite exhibits a tensileelongation of 250% at an initial strain rate of 8.9 x 10^(-4) s^(-1) and at 833 K where anappropriate amount of liquid phase is presented in the composite. The superplastic deformation isuniform and the strain hardening exponent γis as high as 1.6. The fracture surface is intergranualand the superplastic deformation mechanism of the composite is considered to be grain boundary(interface) sliding accommodated by an appropriate amount of liquid phase.