Determination of Johnson-Cook Parameters for Cast Aluminum Alloys

A series of experiments were conducted to determine the Johnson-Cook parameters for three different cast aluminum alloys, namely, A356, A357, and F357. Room temperature compression experiments were performed under varying rates of loading ranging from 10(-3) s(-1) to 5000 s(-1). High temperature compression (235 degrees C and 435 degrees C) experiments were performed at an average strain rate of 5000 s(-1). A split Hopkinson pressure bar (SHPB) apparatus was utilized in conjunction with an induction coil heating system for applying dynamic loading at elevated temperatures. In addition, experiments were performed under high strain rate tensile loading using tensile SHPB apparatus, and the fractured specimens were examined under scanning electron microscope (SEM) to understand the failure modes in these alloys. Highspeed photography was used to capture the chronological progression of the deformation under dynamic tensile loading. The results indicated that all the three cast aluminum alloys were sensitive to strain rate and temperature. A356 exhibited the least value of flow stress under both static and dynamic loading conditions, and the highest elongation before break under dynamic tensile loading. The SEM images of the fractured specimens under dynamic tensile loading showed characteristics of transcrystalline ductile fracture in these cast aluminum alloys.