Microstructure evolution and mechanical properties of rheo-processed ADC12 alloy

Microstructure evolution and mechanical properties of the rheo-processed ADC12 alloy were investigated by means of optical microscopy, X-ray diffraction and scanning electron microscopy. Primary dendritic Al of rheo-casting (RC) and rheo-diecasting (RDC) ADC12 alloys are sheared off. The average size, as well as solid fraction of the primary Al increase with descending pouring temperature. The mechanical properties of alloys are strengthened by rheo-processing. Ultimate tensile strengths of RC samples increase with the decrease of the pouring temperature, and reach the maximum in the range from 580 to 600 °C. At pouring temperature of 595 °C, the RDC sample obtains the best ultimate tensile strength and elongation. Great reductions on porosity and primary Al globularization are crucial to the mechanical properties. Relationships of the primary Al size and yield stress are depicted with Hall-Petch equation.