Microstructure Evolution During Rheoprocessing of A356 Al Alloy Using Cooling Slope

Rheoprocessing of Al alloys has grabbed attention for quite some time now, due to its potential to deliver sound engineering components with superior strength to weight ratio, when coupled with the gravity and pressure die casting techniques. However, effective implementation of the adopted rheoprocessing technique requires in-depth investigation of microstructure evolution mechanism, to meet the demand of producing semi-sold slurry having sought after morphological features of constituent primary solid (Al). A cooling slope is used here to perform rheoprocessing of the A356 Al alloy, to generate semi-solid slurry of the said alloy, for Rheo-pressure die casting process. Rapid oil quenching technique has been employed to investigate the physics behind slurry microstructure formation, while flowing down the cooling slope. Correlations are developed, based on the repetitive experimental results, between the melt flow length and shape, size, density of constituent alpha-Al grains of the slurry in view of establishing process control. Correlation model has also been developed to address the interdependency of particle size and shape, which serves as the quality characteristics of the semi-solid slurry for practical appliances. Insight is obtained on the effect of grain refiner addition on slurry microstructure evolution, during rheoprocessing using cooling slope. Moreover, solute rejection phenomena occur during cooling slope rheoprocessing of the slurry, and final globularization of microstructural features during isothermal holding stage has also been studied in this work.