Characteristics of thixoformed A356 aluminum thin plates with microchannels

A356 aluminum thin plates with a thickness of 1.2 mm were produced via thixoforming process under different temperatures ranging from 585 °C to 610 °C. In addition to large primary α-Al grains, unique fine secondary α-Al grains (equivalent diameter below ~ 8 μm) were revealed through microstructural examinations. These secondary α-Al particles exhibited irregular morphology at 590 °C, which gradually transformed into equiaxed/globular grains at higher thixoforming temperatures of 605 °C and 610 °C. On the other hand, their size (the equivalent diameter of the grains) continuously increased from 3.2 ± 0.16 μm at 590 °C to 8.1 ± 0.4 μm at 610 °C. Energy dispersive X-ray spectroscopic analyses showed that the Si concentration gradually increased within these secondary α-Al grains. A quenched modified morphology consisting of angular and finely branched eutectic silicon was observed at the thixoforming temperature of 590 °C, which seemed that it changed to a fibrous morphology at 605 °C and 610 °C. By increasing the thixoforming temperature, the elongation of the thixoformed plates monotonically increased to 12.6 ± 0.4% at 610 °C, whereas the ultimate tensile strength reached its highest value of 280 ± 12 MPa at 600 °C then experienced the sharp reductions at 605 °C and 610 °C.