Microstructure Characterization and Thermal Analysis of Aluminum Alloy B206 During Solidification

Abstract

The solidification kinetics of a high strength B206 aluminum casting alloy as a function of cooling rates between 1 and 15 K/min has been characterized through a combination of differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and optical microscopy. Three different peaks were detected in the DSC analysis, which corresponded to the nucleation of an α-Al solid solution, an Al-Cu-Fe intermetallic and the eutectic phases. The presence of these phases was confirmed using a coupled scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis. The α-Al nucleation temperature was found to be independent of cooling rate while the eutectic and the intermetallic formation temperatures were depressed by up to 20 K. The evolution of the fraction solid, particularly during the solidification of α-Al was also affected by the cooling rate in such a way that slower cooling was accompanied by a higher fraction solid at a given temperature. Concurrently, microscopy was used in order to quantify the variation in secondary dendrite arm spacing (SDAS) with cooling rate for use in numerical simulations of casting processes.

Prediction and Experimental Validation of Cooling Rate Dependence of Viscoplastic Properties in a Partially Solidified State of Al–5 mass%Mg Alloy

“…Consequently, if the values of A and x are previously known, then the value of α at an arbitrary cooling rate is calculable using eq. (23). Figure 12 shows the relation between the cooling rate and DAS II measured in the current study.…”

“…Viscoplastic properties are assumed to be dependent on the solid fraction in a partially solidi ed state, as reported earlier in the literature 2,14,18) . Increase in the cooling rate is known to promote microsegregation 19,20) and to affect relations between temperature and solid fraction [21][22][23] during solidi cation. By considering the effect described above using a microsegregation model, the current study predicts viscoplastic properties at an intended cooling rate based on previously reported viscoplastic properties 17) .…”

Effect of Si Addition on Flow Behavior in Al-Mg and Al-Mg-Si Molten Alloys

“…The values obtained from experiments differed slightly from those obtained from theoretical calculations for ternary alloys; these differences can be attributed to different rates of solidification/heating in DSC experiment. [19,20,23] However, this difference was very large for the solidus temperature of AM6 binary alloy, which was around 577°C in DSC experiment, compared to 451°C calculated theoretically (Table III). It was found that enthalpy of fusion of the tested alloys increased with increasing Si content.…”

Grain Refinement through Shear Banding in Severely Plastic Deformed A206 Aluminum Alloy

“…This necessity is overemphasized in the case of 206-type aluminum alloys (i.e., A206 and B206), due to their heat treatment complexity which is exerted by the presence of Cu-rich intermetallic phases. [5][6][7] The Cu-rich phases hold lower electrochemical potential and lower galvanic corrosion resistance, thereby, corroding faster than its counterparts in Al-Cu series. Some of the performed researches regarding the severe plastic deformation of Al alloys have focused on the effects of processing parameters such as the accumulative strain, [8] strain path, [9] strain rate, [10] and the inter-pass treatments.…”