Evolution of the semi-solid microstructure of ADC12 alloy in a modified SIMA process

Semi-solid metal processing is a new developing technology. This processing has a more advanced technology than traditional ones such as forming and casting. The quasi-spherical grain has been formed by recrystallization of the dendrites during reheating in semi-solid state. The strain-induced melt activation is simple and does not need expensive equipment for preparing semi-solid billets. In this paper a modified method was proposed based on the strain-induced melt activation process. The microstructure and mechanical properties of ADC12 aluminum alloys prepared by the modified strain-induced melt activation process were studied. Different levels of heating temperatures and holding times were used in this investigation. The results of heating experiment revealed that the optimum heating temperature, isothermal holding time and average size of particles were 828 K, 1800 s and 70 μm, respectively. The results of isothermal treatment showed that the size of spherical particles increased linearly with extending the holding time at the 828 K. In the meantime the quantity of particles showed the parabola descent. These phenomena are in accordance with the Lifshitz–Slyozov–Wagner theory and Ostwald ripening.

Graphical AbstractThe cast microstructure of ADC12 alloy is dendritic crystal in Fig. A. As shown in Fig. B, the grains change to spherical and granular shapes and uniformly disperse in the liquid matrix through a series of processes. The advance and feasibility of the modified SIMA process has been proved by metallographic observation.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We introduce a modified SIMA process for producing the semi-solid billet of ADC12 alloy. ► A good microstructure of semi-solid billet can be obtained at 828 K for 1800 s. ► Kinetics of coarsening of ADC12 semi-solid billets follows the LSW theory and Ostwald ripening.