Investigation on Fracture Mechanism of A356 during Thixo-Forging
Transmission electron microscopy (TEM) was used to assess the microstructural changes accompanying semisolid molding of a creep resistant Mg-5%Al-2%Sr alloy. It was revealed that the processing created thixotropic morphologies with globular solids of α-Mg, having well-developed sub-structures. The quickly-solidified liquid fraction, enriched in Al and Sr, led to the formation of increased volumes of a lamellae type Al4Sr phase, surrounding the secondary α-Mg. Traces of Mg17Al12 still existed, predominantly as irregular shape compounds located mainly in grain interiors. Both the primary solid and high melting point precipitates of Mn-Al modified with Sr, acted as nucleation substrates for secondary α-Mg grains.
C.G. Kang, S.K. Kim and S.Y. Lee
K. K. Wang et al., "Investigation on Fracture Mechanism of A356 during Thixo-Forging", Solid State Phenomena, Vols. 116-117, pp. 140-144, 2006